Reply to One method to Easily Solve the language issue
Fair points. I didn't really consider multiple languages on the same topic so i didn't see it as an issue.
Because... Langauge just on posts... which i'm guessing you guys call forum threads?
Aka don't even have a tag for comments. Generally speaking people that write a post in a language are expecting that same langauge as a response. To account for violations of that practice I don't think is your need to work on. That handles 1,2,3,5
As for paragraph 4 ... why would you need to handle when someone does this? I guess the answer is... allow them to change the language tag.
Much of this stuff you kind of just have to let the community handle... "Hey i noticed you wrote a post in Chinese however you tagged it English... here's how you change it. Thanks."