I think I know what's happening - you're using the edit page a lot instead of the "new post" page.

It looks like I forgot to tweak some of the settings on the edit page, there is a setting there:

HTML in message: Disabled, Enabled with auto-line-breaks, Enabled

You'll have to switch this to "Enabled with auto-line-breaks" for your <img> to work, I think by default it is disabled.

I removed this setting from the "new post" page and changed the default there to enabled, but forgot about the edit post page when I was first setting up this forum.

When I get some time (ha...) to tweak the forum some more, I'll try to remember to update the edit page.

- Michael