A separate comment pool will behave differently if there's a separate comment vote power per account or not. The comment pool idea works best with a separated comment vote power in my opinion. In this way, people with a lot of stake won't see voting on comments as an opportunity cost.
Absolutely. This is more critical to supporting comments than a separate reward pool for comments (although I support that too). There can be different parameters for each vote power tracker too (the parameters determine how many votes to cast per day to not waste your full voting potential).