Here's a test case [non-idempotent.zip](https://github.com/google/google-java-format/files/1380355/non-idempotent.zip) Bisecting seems to implicate 79a39179f8c "Wrap line comments that exceed the column limit" by @cushon, which makes sense to me as a culprit.
Here's a test case
non-idempotent.zip
Bisecting seems to implicate 79a3917 "Wrap line comments that exceed the column limit" by @cushon, which makes sense to me as a culprit.