When I first found out that this was removed months ago I didn't really care because well what difference does it make if there are 20 (like I had on my 3.x site) or 25 posts on a page? Well turns out it actually does make a big difference when browsing on mobile. 25 posts is too much for a mobile site and the browser often crashes, especially when switching between pages.

Since there are now no post numbers in IPS 4, neither you or your browser would know how many posts load per page - problem solved. Ignorance is bliss.

Are you sure it has been removed? I could swear that I saw that option while browsing ACP yesterday... unfortunately, I can't access my localhost installation at the moment due to hard drive failure, so I can't be sure, maybe my brain is playing games with me.

Was a joke... it is in Community >> Topic Settings. Can't miss it.

Lol thanks for letting me know. How the hell could I miss that?