Before I post anything here, I always ask two questions:
I’ve occasionally tried to contribute to dogpile-y threads, and I’ve invariably realized nobody responds to a new, succinct post on page nine, since the arguments that take hold on page one rarely actually stop.
It’s shouting into a void.
You should consider a username change to moderatelyverbose.
Too many threads to fully follow the latest trainwreck. Started in MPSIMS, then branched out off to the Pit and ATMB last time I checked.
Sadly, I don’t have time to figure out which of the multiplying threads I need to be up to date with before I can chime in fully informed!
If the worst of people is on display I’d rather not be privy to it.
This is why. I remember posting in the thread about “do good-looking people have it better”? I don’t remember the exact title. But here is what went down:
My first post: “Yes, good looking people have it better, because X, and because Y. It’s not all the time, but on the average, it is the case.” Wherein X and Y are my reasons.
Someone else: “WHY do you feel good looking people have it better?”
Me: “Well, as I said, X, and Y, and also Z.”
The same person: “But WHY? I still don’t understand.”
And on and on and on and on. And that’s how it always seems to go. I explained my point of view to you, do you have any more questions? New questions? I can’t explain it over and over. Do I have time for this? No. Do I have a life? Yes. I just don’t have time to sit on the computer. I do post at work, but generally my posts take less than 30 seconds. Arguing back and forth takes all day, and I have lots of things to do, and when I get home, I have my real life to live, and it’s not on the Internet.
Sometimes if it’s important enough to me (like the recent kerfluffle on misogyny) I might participate. But that was only because I wanted to speak up and not remain silent, and because some people looked like they might be convinced. I will never participate in a thread where people are just talking at each other and no one is listening.
It entirely depends on the topic, the direction of the wreck, and whether or not I can make a semi-funny joke about it. Piling on just to be part of the crowd is a different sort of juvenile.
I think a lot of times these types of conversations boil down to a few, very passionate people on each side of the issue, who are really only interested in arguing with each other. I assume my opinion is going to be ignored or brushed off as being dumb. I posted in a thread recently where someone asked, “Why might this person be acting this way?” I responded, saying, “Well, when I acted that way, it was because…” Only to have the next person say “Nobody acts that way for that reason.” I must be the invisible girl, then! It irritates me when I share an opinion or a personal experience, only to have people act like I don’t count, or imply that I’m lying, instead of thinking about what I said and actually taking it into consideration. And in the type of thread you’re talking about, that’s a large part of the problem. “I’m right and you’re wrong!” “No, I’m right, and you’re wrong!” Being told I’m a terrible person and then defending myself, repeatedly, page after page, while the opposition sticks their fingers in their ears and says, “la la la - I can’t hear you”? Too much aggravation for me. Maybe I’m just too sensitive. I do say what I think about topics that are important to me, whether I think my contribution will be welcomed or not, but only if the conversation is a civil one. I’m not going to stick around if it devolves into an “is too, is not” fight, and I’m certainly not going to take part in one.
Oh, I just realized the OP was wondering specifically about the more prolific dopers, of which I am definitely not. I think that a well-known poster’s opinion might carry more weight in an argument, but maybe they just don’t want to deal with the drama. And even though I’m not the intended target for the OP’s question, I just typed out this whole response, so I’m submitting my answer, anyway!
Also, those of us who have been here a long time and participated before, you already know our opinions on most things. There are some subjects that I just can’t be arsed to argue about any more.
Some of the best arguments, along with their arguers, are dead.
Dogpiles: once someone’s been told their position or post is straight up stupid, and the error acknowledged or at least not defended, that should be the end of it. Piling on is opportunistic trolling IMHO. I’m probably guilty of taking a bite out of a poster’s carcass once or twice, but it’s not a habit.
Trainwrecks: Is that where you get like 6 or 7 hijacks going at the same time that may or may not have anything to do with the OP? Or is that when you get an whackjob OP that is just defensively and “creatively” batting back all comers in an effort to “not be wrong”? If it’s the latter I avoid them because I consider them trolls who can’t be reasoned with. The former I have no problem with, and I especially love completely derailed threads because they sometimes lead to some pretty interesting things. Like 1920s Style Death Rays.
Yeah, there’s a difference between dogpiles and trainwrecks. I don’t like dogpiles at all - a mob against one or two people is never fair. Trainwrecks - eh. Take 'em or leave 'em.
I don’t post in a lot of threads for one or more of these reasons, and both trainwrecks and dogpiles would probably fall under these:
If the topic is something I know a lot about (or think I do), I might participate in spite of 2 and 3. But there aren’t very many topics like that.
Roddy
I’m not a prolific or long-term poster on this board, but I am on another, and I avoid the train-wrecks there both because it’s just not entertaining and because ‘it’s all been said before’. Which might be the same thing.
On this board, I enjoy a certain amount of semantic wordplay, but it does get dull quickly, especially if it’s on a subject I am not personally involved in. My opinions aren’t unique, and I’m not going to argue someone else’s case, so there’s no real reason to toss the 2 cents in when I can save 'em all up and get a coffee.
I’ve been gone from here for quite a while, but unless there’s been a huge paradigm shift here, I can easily come up with 2 reasons why folks avoid them.
By that logic, we shouldn’t bother discussing things with each other at all. 
That’s the first time I’ve laughed out loud all day! Thanks - I needed that. Today has been a shitty day.
I don’t post a lot, but I actively avoid the crazy threads unless someone says something I feel needs a response and no one else has seized that opportunity AND I’m in the right mood. There’s an active thread now that I read every day that makes my blood boil just reading it, but to respond in it would probably make my head explode. And to effectively argue my point, I’d have to give more personal details than I prefer.
I been in my share of trainwrecks, and I even been the subject of a dog pile. I don’t care about most unless I am personally involved. I made a resolution to myself upon this return to the board that I was not going to get personally involved in any thread. I will endorse my posts, thus the sig at the end, but I am not going to post anything that will make me step aside for a day, week, or year. This place is going to be fun for me, or I am not going to be here.
YMMV
SFC Schwartz
I’m not prolific but I am a long-term poster. I usually don’t catch them until they’re dying out (who are all these people and what to they do that they have all this time to spend on the boards?), so I don’t post unless a) I think more support will help drive whatever home, or b) someone needs support on a hijack. I’ve been in the middle of arguments before with The Stupids, and I’ve wished more people would come and help ram the points home. If I get that vibe from a trainwreck, I’ll chime in. 95% of them I don’t touch.
I haven’t been here that long and I’m not sure I’m especially prolific. IDK how I feel about piling on in general. I can imagine if certain opinions happen to be widely held, it can end up being something of a witch hunt. The only one I’ve been involved in personally was the JOSH fiasco which really a trainwreck-cum-dogpile - the best of both worlds I suppose. Main motivation there though was that I happen to have a soft spot for obvious trolls who manage to skirt the letter of the forum’s rules while butt-fucking the spirit of them.