Things that are annoying about fanfic.net:
1) The new layout is horrendously confusing. I mean, really. It's better, certainly (there's finally a 'delete chapter' function, which has been long overdue), but confusing.
2) The summary section, not content with already stripping the "/" symbol and making pairing notation impossible, now strips the frelling hyphens as well, which just made my update-note look like it was written by someone with no knowledge of grammar. Which is irritating.
I'm sure there are more, but I covered them in stop_the_badfic many moons ago.
It annoys me in general that they have to resort to such methods to stop crappy writers from writing imcomprehensible summaries. They try to make the site more accessible, but they move further and further from their motto ("Unleash your imagination and free your soul!") whenever they do.