What about presenting a zero-sats lightning invoice?
Discussion
Or a Nostr login, to read?
I'm just thinking for our public gitserver. Not your website.
I guess the bots don't bother hitting up websites like Alexandria, since they can just go for the relays, directly. Or maybe they're too dumb, to figure that out? 😅
I like how you think

the issue for the rest of the web is about the tradeoff with being indexed by search engines.
nostr train dont care 🚂
Yeah getting indexed is nice, just as long as it's not most of my electric bill. The other things are you have to expose some things so it's not complicated for the user. I think capchas and stuff like that suck and they really skyrockets bounce rates depending on your market. Plus integrating those services destroys user privacy.
It's always a trade off. If a user can do it usually a bot can do it too.
Imagine blocking nip05 requests...
The GitCitadel nip05 accounts for the next busiest traffic (not a problem by the way just a few kb/s) and I wouldn't want to block that.