What's some double standards in fanfiction that you hate? I'll go first.
The double standard I hate, is how it's ok to ship a cannon straight guy with another straight guy, but I can't ship a cannon lesbian with a straight guy. Do you not see the hypocrisy!
Now I don't care who you ship as it isn't my business. All I ask is that you let me ship who I want In peace and I'll let you ship who you want in peace.
At the end of the day it's just fanfiction, so why do you even care about a random person shipping a ship you don't like on the internet. Here's a really easy thing you can do if you want to avoid it. It's just one simple thing.
Look away. It's that simple. If you don't like it, then don't read it.