I decided that since, unlike email, the senders of messages can't be spoofed in Steem comments, and that account intentions would change slowly if at all, that accounts were a better level of granularity than comments for classification. I do see a lot of merit in an additional layer for scoring individual comments though, and these could in fact feed into an account classifier.

I'm in the steemdevs server in discord, but am not very familiar with it, and also steem.chat as @andybets. I'd be interested in what you're working on. :)