It’s hard to know exactly how many people see them from the stats Reddit gives Mods. Reddit gives a figure within the post for views, which stands at about 160,000 for the post I mentioned. That includes the times people have been served the title in their feed & and the times people clicked on it (sadly Reddit doesn’t differentiate further).
The fediverse site has been going for 6 weeks and has about 620 subscribers. My guestimate from looking at addresses in comments is that maybe 100-150 are reddit migrants. So roughly speaking 1 in 1000 r/futurology people who saw something about our fediverse site were motivated to join.
A sobering thought for people who think the fediverse is about to crush reddit.