I've downvoted quite a few proposals because I thought the synonym should go the other way, or I disagreed with the proposal outright, but I felt like I should say something about why I think that way in many of the cases. (For example, there is currently proposed
[windows-ce] on Stack Overflow.)
It would much more robust, relevant, and economical to allow comments for each synonym proposal right on that page, as opposed to starting a new discussion question on Meta for every single one, where it wouldn't necessarily get exposure anyway.
While it's possible that a discussion on a synonym may end up lengthy, there could be a facility where if the number of comments reach a certain threshold (10 sounds like a good number), then all the comments are removed and migrated to the appropriate Meta in the form of a question (with a link left behind) -- the synonym proposer would own the question (probably best to auto-set it CW), and all comments would end up as comments on the question. (I realize the migration system may be too much effort for a small gain, but it's one solution to the problem.)