These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Scrappy Mechanic: The introduction of 4 character choices in filters. For the vast majority of fandoms the site is used solely for Shipping two characters together. Since the update this ability to add more characters has lead to an infuriating level of people who put all the main characters in a story as the 4 characters even if the story is just for shipping one of them. Example: Wanting to find Spencer/Aria stories for Pretty Little Liars, only to find that filtering for those two characters now also brings up dozens of stories that have Spencer, Aria, Hanna and Emily all included in the filters.
On the other hand, this has now made seeking out pairings like the OT 3 a lot easier, now that one can filter out the fic that deals with just two thirds of the threesome.
It is possible for writers to make pairings which are recognised by the filter. Whether enough people do it to avoid irritating the people who still hate the new feature, however ...
The hatred is somewhat lessened by the introduction of the exclusion filters, which allow you to filter out stories with specific characters and/or genres that you don't want to read. It's especially helpful when trying to exclude a story with an OC (thanks to the newly created OC character added to all sections) in order to avoid a shameless Mary SueSelf-Insert Fic, or exclude a character you don't particularly like. Though sadly, the OC character is a recent feature, so many of those stories lack it, ensuring that a few always manage to avoid the filter.