1. Howcome whenever I blacklisted things I voted down (I used both votedown:myname and voteddown:myname) they never work?

2. Is there a way to search "or" between tags? For instance, searching pics that have cum or doggystyle.

https://e621.net/help/cheatsheet

~tag1 ~tag2
Search for posts that have tag1 or tag2.

Blacklisting tags requires a lot more code than searching for them so most likely we haven't written the code for blacklisting voted posts yet.