When I'm on a tag synonyms page, there's a box:
Suggest a sometag synonym: ________________ [Suggest]
So I type in a new tag and click Suggest.
Often I don't have enough rep in that tag to suggest one, and get an error:
Creating a tag synonym requires 5 score in this tag.
There is a big warning just before the box ("Users with more than 2500 reputation and a total answer score of 5 or more on the tag, can suggest tag synonyms"), but there's no way I can be expected to remember my score in every tag, or go clicking around my profile to check.
It'd be much better to remove the suggestion box entirely if I don't have enough score in that tag, so I don't waste time clicking and typing in a suggestion only for it to be rejected. Maybe replace the box with text saying I don't have enough score.