It’s not so much the number of parties, as smalltalk is OK in general chat, it’s the off-topic noise that is discouraged, because of wasted time/attention, as you said, and possibly disrupted on-topic discussions.
It’s not so much the number of parties, as smalltalk is OK in general chat, it’s the off-topic noise that is discouraged, because of wasted time/attention, as you said, and possibly disrupted on-topic discussions.