I hate when one of my cw starts to flood the chat, especially the #general. It goes like:

CW: hey
CW: anyone have a pendrive
CW: ?

Me: I have one (and tells him where he can find on my desk)
Another CW: I have one too

CW: thanks, I'll get the one from <Another CW>
CW: hahahahahaha

You don't need to write a whole thesis in a single message, but at least you should guarantee that each message have some meaningful information, not just "hey", "?" and "hahaha"

Slack is not MSN.

Who should and when it would be a good time to tell him this is a waste of attention?