I think we are talking about two different things but yes Nostream relays now have a minimum subscription ID length. Gotta ask the Nostr CEO why we have that limitation.
Discussion
Ah, possibly I misunderstood what you meant by clients not supporting it. I'm both creating events with PoW and filtering events from unknown sources by it too. Any less than 16 bits doesn't seem worth it in either case atm though because of that limitation on subscriptions.
PoW on pubkeys, PoW on event ids and subscription ID length are different things for sure and unrelated.
PoW on events is what you do when you try many nonces on your event until you get an event ID with s minimum number of zero bits.
Subscription ID is how uniquely identify subscriptions over the same websocket connection.
Besides that, when querying for authors or event IDs there’s now a minimum length of 4 hex characters or two bytes. So you can search for the prefix of authors or events that start with zeroes but you must pass something like "0000".
Sure man, I get all that wrt the different kinds of PoW.
I just realised I've misread some of the text in NIP13 though which is where the misunderstanding is happening and probably why my subscription wasn't working.
LOL, feeling pretty dumb after that.
Basically, what I said should make sense if you just replace subid="000" with ids=["000"] 🙏