Here's an article about it written in 2011. In almost all regards, the points for email works for the forum as well.if you feel that a post has upset you, do NOT reply to that post. Instead, write down the reply elsewhere. Then leave the forum or topic (depending on need) for 24 hours. Then, revisit your reply. Chances are you no longer feel the need to reply, or will reply in a milder way.
However, if after 24 hours, you still feel as strongly about it, then post it, or discuss it in private. Just be sure you are willing to accept the consequences (if any) of the post. Don't let the reply fester because you feel unable to express it, that's bad for your mental health.
https://www.psychologytoday.com/blog/th ... -hour-rule