Yeah, I, too, found that to be a really odd piece of advice from a security expert. If I were the Brian (but I'm not), I would have asked followers to not trus

Yeah, I, too, found that to be a really odd piece of advice from a security expert. If I were the Brian (but I'm not), I would have asked followers to not trust the site until the certificate issue is fixed, even though I "know" my site is still safe. I think the properly cautious attitude is to consider all bets being off when a certificate is invalid for whatever reason. There is no guarantee what your visitors are actually getting.