Adding tags to answers so people know what the answer is about is trying to treat the symptom of a larger problem: the question isn't specific enough and needs to be revised.
That is, questions should be specific enough to invite (and demand) the correct answer to solve the problem stated in the question. While there might be more than one way to solve a problem, every answer needs to be talking about the same thing.
Otherwise, if I'm talking about apples and you're talking about oranges, having a unified voting system that pits our answers against each other doesn't make any sense. There's no point to ranking two answers that are about two different things in order of score: my answer about apples is correct (for apples) whereas your answer about oranges is equally correct (for oranges).
Treat the core problem—making questions specific enough so all answers are about the same thing—and this feature becomes unnecessary. While you should work this out on your meta discussion site, that might mean qualifying questions on Chinese.SE with the dialect:
- In Mandarin, what does X mean?
- How can I phrase Y in Cantonese?
- Is there a word that means Z in Taishanese?