[ ] Summary statistics at end of a search, like we have already for a thread ("Authors/@mentions of visible messages in this thread"). [Requires generalization of threadAuthors/threadMentions mechanism to readMessage]
[ ] In search, ideally we'd also get a count of number of distinct authors too, like we currently do with threads. Combined with searching by root post (#364), we could quickly compare SOLVED vs. OPEN solving students.
[ ] Can we also get a list of people that don't appear in a search? I.e. detect the zeros. Superuser only?
[ ] Alternatively, superusers could have an option to get the data (including zeros) as a CSV row or column with a consistent user sort order.
threadAuthors/threadMentionsmechanism toreadMessage](moved from #364)