Yeah, for a fair comparison the standard definition of "active user" is just viewing posts. Not sure why Lemmy sets the bar so high. Maybe they don't care about vanity stats - besides mild curiosity, I couldn't care less.
Posting or commenting seems more like "contributing users" and posts like this just encourage unhelpful noise.
If people use it and they don't post or comment, it could go dark ( i.imgflip.com )