It’ll just lead to a general decline in sub quality.
Even if not, it should be fairly simple to make an extension or userscript that does it. All the necessary data is already on the page. If Lemmy really does blow up I’m sure we’ll get something like RES that gives us more frontend customization options.
Okay, but this is the problem the fediverse was created to solve. If someone starts doing dumb things, we just defederate from them. No need to freak out about it.
The only thing this does, IMO, is highlight the need for easy instance migration, just in case the one doing dumb things is your own instance owner.