So, I have used the related post system on more than one occasion. I did this because I typed in a tag but didn't want to go through the posts in order. I felt like if I went through them in order, I wouldn't be able to enjoy anything that was stuck in some obscure middle page. I wanted to be surprised. But every time that I use that system. I always get some random post that has less then two tags in common with the picture before that. What is the algorithm that goes into the whole selecting of a "related" post? Is there a way that it could be fixed to only include posts that have a certain number of tags in common?

Related posts just sends you to the next, previous, or a random post out of ALL posts on e621, it has nothing to do with relation to the tags, despite the header.

"Sets with this post" is the most related of all of them.

But yeah, that header should definitely be changed to something less misleading.