You are aware you can change that in the options tab, right?
Uh, yeah, if the posts per page is high that means it'll take that much longer to load the page, which is why the sig limit is usually stricter for places with higher post counts.
The post count per page option isn't definite in forums, the option is there so that if there is someone having problems loading a page, they can customise it such that it isn't a problem for them anymore.

So quite frankly, the reference to ppp was unneccesary.