Ok, small attachments (frame of a comic) worked fine.
Attempting to attach a photo resulted in a blank screen after hitting "post", with no trace of text or photo remaining once the smoke cleared.
This is due to the size restrictions perfaps? I was easily inside the file-size restriction, but maybe not the pixel limit...
It would be nice to have an automatic re-size option if that is the case, to save having to do a 1-off re-size on any image I was to post.
