What best support the inference that tan believes nonstandard english in no less valid than standard english?

Yes, just because one had a disability doesn't change the meaning of the word. they would most likely have an (whatever language) sign language to sign what's going on. it would be the same even if he was blind.

is basically a good source of getting and others by what you know for example if someone asked a question and you know the answer you could answer it and get some points or if you need on a question you could make a post about it and wait till someone answers it or just look up the question and see if someone else has asked about it