People also do the opposite - writing a toplevel comment to discuss (berate, more often than not) multiple other comments - 'I can't believe the nattering nabobs of negativism that have been commenting here, etc'.

In both cases, writing a good, non-repetitive, non-meta toplevel comment is probably better but it's more work and potentially unsatisfying - a lot of the time, a comment like that will in fact be lost in a big discussion.

Probably not on the busiest posts (though those are something of a conversational lost cause already), but on most typical discussions without excessive comments, yes.

I'll admit to tailing dang's comments periodically, or searching for specific terms when people challenge / inquire about my own takes on comments. (Most often in the case of dupe / non-dupe article submissions, occasionally others.)