I know I'm 12 years late to this party, but I can definitively answer this question!
I was a developer on the WPF team back in 2005 and we had a tool (FxCop???) that automatically scanned the code and generated bug tickets for violations of naming conventions. Now I didn't originally create or name this property, but one day one of those tickets landed on my desk complaining about "Focusable" being a bool property not beginning with "Is". I renamed the property, fixed everything it broke internally, and followed protocol and sent out a "breaking change" notification to the appropriate e-mail distribution list saying "speak now or forever hold your peace" and waited the prescribed 5 days (or whatever it was) before submitting the change. During that time I receive no response from anyone. Then on the big day, before committing the change, I sent out one last e-mail saying "ok, nobody complained so here I go...". And then the responses started coming in! The big complaint seemed to be "'Focusable' is not a word!" I replied with examples like "But Baush & Laumb use it on their web site talking about binoculars!" or "Other frameworks use the term" and finally "If I don't change it to 'IsFocusable' it will still be 'Focusable'" - still the bickering on the e-mail thread would not stop. And as luck would have it the hard drop dead date for any public/breaking API changes was the next day, and "Focusable" was forever cast in concrete.
I know it's likely no one will ever read this post, but it's always bugged me!