When I upload files to BB, I often select the file (or drag and drop it), then hit tab until the 'Upload' button receives focus, then I hit enter. Recently (I think a month ago), it started showing multiple uploads, resulting in image references within references, or sometimes adjacent references. So hitting enter is uploading it 2 times. Whenever this happens, it makes me look like a bad commenter when really it is BB being buggy.
In image 2, you see 2 file upload progress bars. (It would be nice if BB supported multiple upload, but that is feature request I will save for later.) It shows a duplicate reference to the file being uploaded.