No, I mean the bitcoin block height. Like this:
780,810
Clients don't support changing font size (as far as I know) and it's just text on the bottom of the note so it's not different or special in any way.
—
Developing https://nostrgram.co/ #Bitcoin
Discussion
Ah ok. That's an interesting idea to be able to add replaceable tags. Love that. I'll see what I can do.