Update to E7. A techie at WordPress composed special code to fix the problem I mentioned in E7 about the public display of E6 I was upset about. At first I thought that this was a one-off workaround (something I could possibly have come up with myself, if that was all I coveted…), whereas I wanted a permanent solution. In other words, I didn’t want to have to embed this code every time I wanted to link to a Vimeo video. Also, I assumed that if they had a solution that did work universally, they would just make it part of the code for the entire platform, which would mean it would get fixed in my posting automatically, like any bug fix.
There’s some reason that I don’t quite get for why they can’t incorporate my code into the general one, but it’s still true that I personally don’t ever have to deal with this again: my future Vimeo links will all be as correct as S3/E6 (from last November!) is finally.