It is perfectly legitimate to comment on a suggestion, particularly if disagreed on. This has been discussed in several suggestions already by the devs - it's the only way for people to disagree with a suggestion as Likes only show agreement (and not showing likes doesn't necessarily mean disagreement). As for the argument that if someone doesn't like a feature you just don't use it and (sort of implied) that you shouldn't argue against suggested features, there is the issue of bloat. The more that's added to the XenForo core, the more bloated it becomes. So it's not unreasonable for people to post disagreement with suggestions (as well as agreement) so that the devs can better gauge what to add based on popularity as well as practicality.
Yes, 6 people did like the other thread, though do note that several disagreed with it (they posted to say so).
I think
@Brogan's response in that thread covers this in part:
along with what I previously said:
Anyway, this thread is now closed as a duplicate so I guess the discussion can continue in the other thread.