I'm an Indian and all my life I've pronounced 'often' with 't' silent. Since we follow British English, I assume British people say it the same way? I guess in American English, one pronounces it with 't'. What are the rules about this word in other varieties of English?
I'd say that it's a dialect thing. I often hear people pronounce the 't' in 'often'. It annoys me, because I grew up with it silent, but it's not actually wrong in any sense.
I'm British, by the way. I hadn't noticed it (the pronounce 't', that is) being an American use at all (but now I probably won't be able to stop noticing it). It seems to be increasing in Britain, though.