AutoHotkey's MouseClickDrag with a between-times check are what comes to mind. As a warning, this could be very painful to set up lol (as in, expect lots of trial-&-error).
Steam itself doesn't appear capable of setting such an automated restriction, as far as I know.
It just keeps getting better and better. As far as I know, it pioneered quoting parts of messages inside replies; I wonder how many other chat apps will catch on and mimic it.
I can't find anything about this actually being open-source, so I'm inclined to stick to Boost for Lemmy by Mayayo...