Mudcat does have an "edit after posting." You simply make a new post, explain what was wrong, and post your corrected version. If needed and appropriate, a sincere apology is acceptable.

Example:

In my post at XX:XX pm, I said "You're a horses ass."

The statement was meant in the sense of an analogy and I really should have said "You look like a horses ass."

I apologize to any horse who might have been offended.

Politeness might require any horse who objected to indicate acceptance or rejection of your apology in his/her own subsequent post, but a truly polite horse usually will just quietly accept it and proceed with the discussion.

It's called having a conversation.

John