Considered breaking change because JSON serialization will change, and JSON is used quite often.
replyReordering fields without changing their ID is indeed a non-breaking change from what I understand, albeit quite a useless one :)
> a useless one
replyIf you have a (long) list of fields and you want to keep them lexicographically sorted, being able to reorder is quite useful if you rename a field.
Renaming is forbidden though (because JSON and textproto). In Google, it's a documented antipattern to try to make protobuf look "nice" by changing field indices, rearranging fields, etc. — the common ground is that it's better to not do it.
replyDepends, if you use textproto then renaming is problematic too
replyShit, you're right, I'm trying to remember the one that used to trip us up all the time, maybe it was removing fields?
replyThere was definitely one that kept tripping up the checks and it was something people like to do.