Maybe I'm the wrong sort, but I would never wear black tie to an evening wedding without being told to. And I do think it would look incredibly odd if you were the only one outside the wedding party wearing a dinner suit. In fact, I think it would be construed as very rude. For the same reason, I would never wear a flower in my lapel to a wedding unless I was in the party.
This seems somewhat contradictory. In one post you say you don't care if you're the only one in black tie but then you say that you'd feel odd if you were. In the first quoted post are you talking about events other than weddings while the second is specific to weddings? Or is the idea that once the invite says BTO you're assuming there will be at least some other people in black tie and it's just fine to bust out the tux?