I don't know about doing it in comments. It might be best not to given how the comment section works. (I think it would be very controversial) It would be better to add a link out to the image you want to show people.
But in the forum you can use BBcode to post images. You have to host the image somewhere else. so you would just write in the url to the image and when the page is downloaded the viewer fetches the image from your server not JapanesePod's server.
Does that make sense?
There's a link to how to write it up here
http://www.japanesepod101.com/forum/faq ... e=bbcode#9
When I have added images to my forum posts I try to make them as compressed as possible. Not everyone has high bandwidth connections. a couple of Kbs might be ok but MB sized pictures might be a bit much.[/img]