I take it that if someone writes a fair number of good Excel answers in a respectful manner, they might get noticed, nominated for MVP by an existing MVP (or admin?) within some sort of forum, and validated as an MVP by a quorum of existing MVPs.
That's pretty much it. You don't have to be a world-renowned expert w/ respect to etiquette, not everyone enjoys every single post I make, to be sure. But this is a community, so being a disruptive force in our community isn't exactly conducive to being appointed as a MrExcel MVP, here.
To really simplify this, it boils down to being a community leader, here. As this is a technical Q&A group of forums, for the most part, technical expertise is certainly a factor. But being a community leader also boils down to demonstrating a long-term commitment in advancing our community through participation.
And the type of participation in question will in all likelihood will not go unnoticed, our MrExcel MVPs aren't just posting, I think we tend to read quite a lot threads just for the sake of reading them. I know in my case, I read a lot more than I post, because I'm still a student of the game/a curious individual, and my role here kind of makes this necessary.
And quite right, the appointment is then verified by our body of current MrExcel MVPs, in an anonymous manner. MrExcel MVPs are typically confirmed by current MrExcel MVPs in a landslide type manner, i.e., there's no doubt about it.
Hope this helps.