Right now, most of the time we don't see which moderator banned this particular user and mods sometimes forget to give reasons while banning. They must be always required to give reason while banning each user.
it would be nice to always see, which mod banned a user.
While not the most user-friendly UI (good luck paging through the history,) if you go to /admin/advanced/events and search for user-ban, you can find out who performed the ban, but not the reason (nor any duration, actually - the test below was a ban for one hour; there's no discernable difference between this and one of our spammers.)

Already we have this suggestion: https://github.com/NodeBB/NodeBB/issues/6290
I think it is a good idea.
Thanks @mohammadhassan99 -- we'll track it there.
For the record I also think this is a good idea :+1:
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For the record I also think this is a good idea :+1: