Oddbean new post about login | logout Exact count is a psyop. There is no global. Few.
It's the bandwidth more than the count I have beef with. A relay can already give you a count with a few bytes, and it will be equally as inaccurate as trying to fetch them all individually
The personal and local relays will soon all be syncing, based upon some criteria (like a follow list), so you'd have the reaction events, already, from the npubs you actually care about, and can just count that. If you want more info, for some particular note, you can look at an aggregator website, like nostr.band, or ask an API. I only see when my frens react.