But not everyone agrees with you that it is spam. So your logic is flawed, and your condescension is inappropriate.
How do you know he would never post again? Maybe he would have participated in the rest of the thread, answering any questions with detailed knowledge. Maybe he would have seen some other threads, and joined that discussion. Maybe he would have become a useful long term member of this community. But we’ll never know, because you banned him after one post.
I’ve not seen the post in question. What exactly did he say that you find so offensive?
Phraseology might make a di9fference. Suppose he had said:
“I have recently researched this very topic. Here’s my paper on the subject.”
Would that have been acceptable?
Seriously, stop acting all befuddled. No one is advocating for more spam. Are you even reading for comprehension in this thread, or just being willfully obtuse?
Hell, yes. Spam is unwanted material.
If someone contributes to a thread in a “fighting ignorance” manner, whether self-promotion or not, it should be a good thing. Yeah – at first glance – it may look like spam, act like spam, but it’s not spam and we are diminished if the post is removed.
Maybe he thought that stating it was his own paper would lead people to dismiss it out of hand, to consider it just another opinion rather than a properly researched paper? Perhaps he knew that the paper offered insight into the question but just didn’t have ego enough to want any credit for it?
What I’m seeing here is if you see a question asked and have some expertise that might provide an answer, don’t join up here to answer it because it would be some anal interpretation of spam.
Seriously guys, rules should be an aid to a good message board but not the be all and end all, and calling that “spam” shows a lack of good old common sense.
If you want your spam that bad, you can have it. I’ve lifted the ban and restored the post to the thread.
Useful hint. If you bite a post and it’s not soft then it’s probably spam. 
You are.
They’re wrong. It’s spam.
Not in all cases. It’s still spam even if you really want to buy Viagra or watch streaming sports.
Wrong. He posted relevant information to a general question for fucks sake. Common sense seems to be lacking in your reasoning here. And if you’re so confident it’s spam why don’t you take it down again and re-ban the poster?
Can’t find the thread now but I remember one discussion about voting methods and we had a new guest join in to describe work done at some democracy research group he was part of. AFAIK, it was the only thread he participated in. It would be shame if stuff like that is considered spam.
Thank you. That was a horrible decision and reversing it was a very good call. I sincerely appreciate it.
Exactly. How could anyone possibly have a problem with an on topic reaseach article where the author gets no financial gain from posting it?
My upcoming book will explore the issue in detail.
In addition, the guy actually paid for a membership so his little stunt cost him $15. If he’s a spammer, he’s doing it wrong.
Ha. If they all did that I fear the SDMB would rethink its anti-spam policies.
He didn’t pay for a membership. If you ban someone and unban them, they end up by default as a Member. It’s a bug in how our software is set up.
My mistake. Thanks.
No they’re not.
No it isn’t.
Really?
To get back on topic:
I think that what many posters are saying, is that while it walks like a duck, talks … etc. in this quite special scenario: It isn’t a duck.
What the mods are saying is: We ban ducks.
For once both are right. 
My take: if it isn’t for direct financial gain & mildly interesting & not part of an organised effort to fill the internet: not spam.