There is no direct route to complain about another user, but you can report a post as abuse, which will lead to a moderator assessing it. If they find it to be abusive, this will lead to its removal or editing. For repeat offenders, or particularly bad posts, Atlassian will reach out to the person who is posting bad stuff, and ask them to get back within the guidelines, try to find out why they're being bad, and even offer help improving their tone or language.
The moderators evaluate a post based on the community guidelines so you may want to read through those and be specific about which part you think the poster has broken the rules on (there's also rules on partners that some of us have to stick to on top of the general guidelines, but they're mostly about not overdoing the advertising)
You may find posts breaching any rules being removed - there are bots here that try to stop spammers and insulting/abusive language is one thing they pick up on
To report a post, hit the ... menu to the right of the header of the post (the line with name, badges and date has ... to the right)