does it actually work or just on a signal relay?

It works on ALL relays.

Interesting - I haven't try that yet. Then again I really don't feel the need to delete anything. But good to know 🤙

I don't use it very often but it's always good to have it handy in case you feel like cleaning your timeline. Maybe you posted something that you later decided it wasn't appropriate. So you can always go back and delete it on ALL relays. Nostr event deleter even allows you to delete your note from specific relays.