Ordering messages is not enforced on Matrix

[remram44]

When forwarding from Gitter to Matrix, it is possible for the homeserver not to handle requests in order, which can mean the messages are posted out of order. Particularly possible since we do multiple API requests to post (invite, join, post).

[remram44]

Should be mitigated by 37329cc since now every user doesn't have to be invited, then join, then talk.