IMO- The greatest insult is the complete absence of replies whenever someone posts in the Your Playing section or wherever (negative feedback/ constructive criticism at least implies someone has taken an interest).
FYI- there are currently over 1200 threads with zero replies in the Your Playing section alone (that's a lot of discouraged drummers right there).
I completely get that. Accordingly, I try my best with the time I have, to reply to as many as I can. That said, there are also some that I don't reply to, unless there's something exceptional going on. For example, players who don't engage in any other part of the forum, but just post a link to their cover on as many sites as possible. I get the promotional reasons for doing that, but equally, I feel no obligation to respond. TBH, I have little time for drum covers anyhow. Someone who takes an active role in the forum is another matter all together. Similarly, someone posting their playing for the first time, whether an active forum participant or not, gets a response from me more often than not.
I'm always positive, never negative in terms of my general demeanour, but there are sometimes negative aspects to what I have to say. Sorry, criticism is negative by it's very nature, but should always be delivered in a positive & supportive way. Saying overtly positive things for the sake of it may indeed be an insult in itself. There's a fine line to be drawn, & every context is different. Clearly, you're not going to use the same bar with a seasoned player than you are with someone who is very early in their journey. Similarly, you're not going to react in the same way to someone who proclaims they're a superstar drummer as you do to someone who is humble in their presentation.
Be happy in your shell, & encourage others to be the same, & you'll not go far wrong.