Add a configuration setting for Thoth to act upon comment threads

[remlaps]

A big curation gap is the lack of automated curation coverage for organic engagement in comment threads. A Thoth operator should have an option to post some sort of curation content around high-engagement comment threads and to direct blockchain reward settings to the participating account(s).

This would require a substantial design change, since multiple authors can be included in a comment thread. Unfortunately, it's nowhere near as simple as reusing the same logic that exists for top-level posts. It should definitely be in the long-term roadmap, though.