While I think you might be on the right track with respect to Wikipedia, this wouldn't really work in casual (or even scholarly) discourse. There are a lot of things of which I'm confident and don't have an immediately available justification, and tracking them down would be so time-consuming that I just wouldn't bother to comment on anything.

Also, there is a disanalogy between Wikipedia and other kinds of scholarship; Wikipedia does not allow original research, in which the appropriate citation for a claim might be the preceding argument, and so should not be explicitly stated.

There are two cases where argument from authority is still clearly fallacious:

1. respecting the authority of someone who is not an expert in the appropriate field - for instance, taking the Pope's word on evolutionary biology

2. regarding the authority as itself what gives truth to the claim - This happens, for instance, when one makes appeals to one's own authority. If someone asks me for a citation and I say "I'm an expert, and I say so" then that's insufficient.

P.S. You should change that URL to a link so MarkDown doesn't eat it.