It looks like the broken BBcode means that you can't even post an inline image that's stored elsewhere; if you want to share an image, it has to be uploaded here. Unless there's some trick I'm not aware of.
(edit: apparently it's been so long that I'd forgotten the BBcode formatting! I was using < instead of [ - once I fixed that, it did work.)
Looks to me like the site is pretty well abandoned if such basic functionality (which should be able to be easily fixed if it's just an SSL issue) has been broken for months.