Which has it's own set of problems, btw.
Try to find an API for "delete".
Oh, and I'm eager to see how their API survives mutual parties extending it. (There is a reason why namespaces exists)
http://matrix.org/docs/spec/#m-room-redaction is the current API for removing messages.
Matrix uses namespaces for extension to survive mutual parties extending it (http://matrix.org/docs/spec/#events), and we haven't seen any problems there yet.
That said, Matrix is still beta and we certainly do have a whole bunch of other problems :)
One of the complainers is matrix (https://matrix.org/), which does JSON over HTTP.