Thread title basically explains it.
I see a thread I might be interested in contributing to, but it has 400+ comments already. It is more than a little daunting to post after that level of discussion has taken place, especially because I’m sure anything I’d be interested in saying has probably already been said.
Am I just thinking into this too much? How do others approach this issue?
I read (although do not post on) another forum where there is a strict rule that you must have read the entire thread in order to post. I try to follow that rule. If I haven’t read the entire discussion, then I don’t make a contribution, because I don’t know what has been discussed before or where the conversation has wandered. The exception might be an IMHO thread where people are describing their particular experiences, which I might skim to see if there is anything interesting or relevant to me before posting my own answer.
As a shortcut I use some of the time (not always because I tend to avoid threads that are that far along) is to “Edit --> Find on the Page” and put in a keyword I was planning to use and look through that way. A hit would need to be read for whether my keyword was in a post I would be duplicating or at least doing little more than paraphrasing.
That may be more work than you wanted to do, but it might save some time in the long run if you really like the thread title and OP.
Why not just read the thread and if you don’t have anything to add to the discussion don’t post and be satisfied that you got to read an interesting subject?
I usually don’t. I stay away from GD most of the time. Exceptions are CS/TGR, where it’s easier to talk about a game or TV show as the conversation isn’t as linear.
But if you need to make some point, make sure to Ctrl+F and see if it wasn’t already mentioned several times as mentioned. Also, you might want to change the number of posts per page. I believe the default is 50, I upped it to 100 and you can go higher.
Well that isn’t a rule here.
I may scan through the posts to see if someone has made the point I want to make and/or if people have refuted it or made interesting points along those lines. Sometimes I’ll just read part of the first page, the last dozen or so posts, assume my point wasn’t made and make it.
The thing is, at least half the time very long threads aren’t any kind of actual discussion of the points of debate. All too often they degrade into either two people shouting past each other, or one idiot/troll continuously arguing already refuted positions and refusing to read or acknowledge anyone else’s points. There are a couple of people on this board infamous for this, yet time and time again they drag down threads and people keep arguing with them! :smack:
And really, there would be no point forcing yourself through all that crap just to ‘earn the right’ to post in that thread.
First!
It may not be a “strict rule” here that you read the entire thread before posting, but it is certainly customary. It’ also courteous.
But, once you’ve done that, jump right in! We were all noobs once 
Welcome to the dope, fir3drill!
That’s right - everyone* who posts puts thought into what they want to share with the group, and to just ignore their contributions is indeed discourteous.
Yup.
*Well, most posters.
Read the first post, pick out a tiny speck of data that interests you, and post:
“all this is very interesting, but aren’t we wandering from the topic, guys? <ThreadStarter> wanted to know about this! …”
and off you go, bulldozing out a new tangent.
I’ll give you courteous, but customary? There are far too many instances of people not only repeating information already shared in the thread but doing so in an aggrieved or incredulous tone that they’re the first to mention said fact.
If people refrained from posting for fear of me-tooism, activity would grind to a near-halt.
Length of board tenure does not have independent predictive value in determining worthiness of posts, so have at it.
Indeed. The best examples of this are when someone revives a zombie thread to post a comment that they already made in that thread three years ago. 
I haven’t read over the thread, but I just thought I’d point out that this is covered in a sticky.
Several of the longest are actually NOT supposed to be any kind of debates, although none of them is in GD: the weekly MMP, the Workplace gripes and the monthly Minirants.
If you drop by the MMP, beer and chocolate are always welcome but not required; posts are not supposed to be particularly relevant to the rest; the MMP is “stuff that’s too mundane and pointless for the rest of MPSIMS”, the only way it can go off-topic is by we all forgetting to open a new one. The other two are supposed to include gripes.
Nicely constructed.
So as you can see, OP, you can also insert sidebar posts that may not be relevant to the thread at all.
Roddy
It’s a very sad fact that many of us can’t remember what was said in a thread that we read only a couple days ago.
Tell me! What may be worse is to post in a thread and then look back over the other replies and see you already said what you just posted – only a day or more earlier. I’ve done that in threads I started. And if a post is more than three sentences long I feel obligated to preview to remove the dupes!
People miss stuff. And just because some people are rude enough to post to a thread without reading it doesn’t mean its bad manners.
I love reading a zombie thread, not having realized it’s a zombie, and seeing a really great post…and realizing that I was the one who had made it!
… and being all, “Damn, that person is good.”