>>bragr+C4
I think it's a capacity problem. Right now, the "system" (legit HN users) have the capacity to deal with dull and inane comments currently provided by dull and inane human commenters. If the dull and inane comments become automated they can arbitrarily increase their number until the system lacks the capacity to deal with them.
If there was one or ten bad comments on this thread - no problem. What if there were ten thousand bad comments?