I suspect it's due to some change in the publish process as I've been migrated to the new TypePad platform. Thankfully it wasn't seen in existing content, only new posts.
It wasn't a problem with posts done in TypePad's own web based Composer but I use the off-line editor BlogJet. A quick trip to the BlogJet support group revealed the answer. BlogJet has an option to "Replace with Typographic characters" and disabling that eliminated the problem.