A family of Microsoft word processing software products for creating web, email, and print documents.
UPDATE: I have a solution (though no explanation) :)
This was caused by some bug in the default Normal.dotm (and NormalEmail.dotm for Outlook). I deleted them, Word created new versions, and the problem is gone!
Found this because some eager digging, trying different templates where I could not reproduce the issue. Even simplified back to creating a new document with the "Single spaced (blank)" template that is almost an exact copy of Normal.dotm (just with less spacing in the "Normal" paragraph style. This lead me to believe the issue was with Normal.dotm. After disabling it (renaming to ".dotm_"), Word re-created the file, and now the problem is gone!
Would someone at Microsoft be interested in looking at my original Normal.dotm to try to debug?
I have kept the file and I'm able to reproduce the issue using that template.
Best regards,
Henrik