One of the authors of Flow offered to answer questions, but their comment is greyed out as a dupe (and it isn't a dupe - something went wrong):
The problem was that there were two identical comments, the software killed one as a dupe, and avik deleted the other one. The software tries to fix this very scenario—it normally would have automatically unkilled the remaining member of the pair. But there are some corner cases where that doesn't work, and avik seems to have outsmarted it.
We'll take a look and try to fix the fix.