When you get an error while posting a reply, but eventually succeed, the reply is posted twice.
Steps to reproduce:
- Open the reply tool for some comment
- Do something to get an error. For example, disconnect your wifi. On (on Beta only) type "is stupid" to get an AbuseFilter error.
- Fix the error (reconnect, or delete that) and save your reply.
The reply will be posted twice, or multiple times, with one duplicate added for each error you got.