The following text is shown about voting and suggesting tag-synonyms:
Users with more than 2500 reputation and a total answer score of 5 or more on the tag, can suggest tag synonyms. Users with a total answer score (total upvotes minus total downvotes) of 5 or more on the tag, can vote for tag synonyms. Suggestions will be automatically approved when they reach a score of 4, and automatically deleted when they reach a score of -2.
I think this is fair for tag with many questions (because that probably means there are also many users who can suggest edits and vote on them). For tags with fewer questions (let's say 60 or fewer), the bar is set quite high. Combine that with the fact that almost every user can create new tags, there are quite some tags which could be considered synonymous, but there is nobody to suggest or vote for that to actually happen.
Perhaps it would be an idea to change the requirement on suggesting and voting on tags.
One way would be to make the requirement dependent on the number of questions associated with the tag (so more niche tags can be voted on by more non-experts on the tag).
Another way would be to allow users with X reputation to suggest synonyms regardless of their score on the tag and users with Y reputation to vote on this (where X is around 10K and Y around 20-30k).
Another third idea would be to let users with 10K reputation suggest tags (regardless of their score on the tag) and allow those users to vote on it as well. The voting process would be different, everyone would upvote with their reputation and downvote with MAX(reputation, 15K). A synonym is accepted when the sum of votes exceeds 100K and is rejected when the vote gets below 25K. (the numbers I chose are just to give an indication of the idea)
This question is meant to see if this is something the community likes, please post ideas in the answers. This is not a feature-request (yet), because it's unclear if this is something the community wants at all and it's unclear as of yet which solution is preferred.