I edit a lot of posts every day. I often run across posts with 'Hi' and 'Thanks' on the top and the bottom of the post respectively. I also run across things like:
Should these items be removed during the editing of the post by an editor?
I am a die-hard thanker. I always end my questions with the phrase "Thanks so much!". (I do not start questions with "hi" for various reasons)
Game-theory is what mainly dictates my approach. This is an interesting situation to apply game-theory to:
Conclusions(based on acceptance of all three assumptions)
If you accept assumption #2, then fewer answers would exist if people stopped thanking. This probably eclipses the problem of clutter when holistically looking at the overall best interest of the forum.
Interestingly, if you disregard the weakest assumption, assumption #3, then people should add "thank yous" when they ask questions and then they should be edited out later after the question has been satisfactorily answered.
If the forum was full of people like me, assumption #3 would be incorrect. But I've talked to very many super thoughtful and intelligent developers who never ask questions on this forum because they are afraid of backlash. And it seems very many other questions are asked by people who brazenly post questions that are not well thought out and detract from the quality of the forum. These people are likely more insensitive to the needs of others and likely care a lot less about "backlash".
If you disregard assumptions #2 and #3, then people should not say thank you at the ends of questions and if they do, they should be edited out.
I feel enough like a robot. Please let us feel like human with a little "hi" or "thanks". There is nothing wrong with this I think... No, don't remove; especially askers may use "hi" or "thanks".