Another pet peeve is when the story is intresting and divided into parts. But even after 5 parts story has not proceeded with the speed like it should.
I doubt any of us are professional writers. Most of the stories are written by members who do it for their own pleasure. And that means they are probably engaging in writing down personal masturbatory fantasies. Nothing wrong with that it all, it's quite fun in fact.
But that means that stories will often proceed in a similar fashion, dwelling on a particular aspect that tickles the author's fancy, skipping over parts to proceed to the next scene of interest, much as what happens in dreams or fantasies. And many stories do abruptly end, just as in real life fantasy, things of the mind often end. Either by petering out or in a more abrupt fashion, as a climax of sorts.
On Speculumpages we edited several thousand stories and received, but did not use even more, and this is what I observed the general pattern to be. This is normal for stories written by enthusiasts who are doing it for self pleasure. Once you start getting paid then it's a whole different ballgame, but in my opinion, amateur written porn is far superior to commercial written porn, even if the formatting is sometimes a bit off.
Besides, if you really like the story itself, (re)formatting with a word processor is a piece of cake.