The ability to edit signs that aren't waxed is not protected by claims.

Really?
Thanks for reporting.

Are you sure you didn't make an exception for sign interaction? They're protected for me just fine.

An exception in the config file, or the config menu? There are no mentions of signs in the config file and I couldn't find an option that affected signs in the config menu either.

I also seem to have forgotten to mention that this is on the fabric version.

You can make exceptions for any block. That would at least partially be done in the main config file.
If you can post your main config file, I can take a look.

Ah, I found the issue, someone did make an exception for signs in the config. Sorry for the trouble.

Now I just need to figure out why so I can get rid of it.

I see. Thanks for confirming!