It's certainly useful, but then a declined flag isn't a big thing either and this feature would be hopefully needed in only a small number of cases. It can probably be low priority.

It actually can be a big thing. Currently, the requirements for obtaining abilities such as the curator ability, are quite high. One declined flag can make a difference.

I'd like to put forth an example: just now, I flagged one of my own posts to request a tag merge (can't think of a better way to suggest tag merges that is possible with today's tools (except for in chat)). Only afterwards, I realized that one of the tags I requested to merge with the other one, was created by me when I made this post, and that it's the only instance of this tag being used (I missed that when creating the post 5 minutes earlier). If I already had the curation ability, I'd have noticed this on the tag merge page. Even then, it wouldn't have been a problem anyway. So even if I'd made the exact same error with the ability (making errors is bad, but inevitable), the consequences wouldn't have been bad in any way. In fact, they'd have been better than when flagging was my only option.

Quoting myself:

(can't think of a better way to suggest tag merges that is possible with today's tools (except for in chat))

Well, creating a post on meta, is another option, but I prefer to avoid it for really trivial cases that are obviously trivial beyond any reasonable doubt.