I haven't been able to post ANYTHING for a while now. When I try a message pops up saying I have to be logged in or I can't use this feature (something like that).
This has happemed to me on several occasions when it took me a long time to compose a post. When it happens, there is a button you can use to "select all," use that, copy and navigate back to where you want to post a reply. Then paste it in a new panel.