I've been reading the dev mailing list for a while, and I thought it might be a time to try and get involved. I took a look at ticket #279 (https://issues.apache.org/bloodhound/ticket/279), in which images in ticket descriptions turn up in the activity feed as well.
The first solution (not rendering them) is simple enough as far as I can see - I've attached a very simple patch which just sets them display:none in CSS.
I've been looking into the second solution (resizing the images to fit instead of hiding them) as well. As far as I can tell (prompted by Gary) the trick would be to do something with the Image() macro in the specific context of the Activity feed to apply the 'span4' class to the img tag. I haven't quite worked out how to do that yet, but thought I'd send a message here before I persisted.
Which approach is preferred? As far as I can see, the question comes down to whether the activity feed could end up misinforming people due to missing images, and whether it would look jarring if a referenced image wasn't there. On the other hand, even resized images might still be very long, taking up a lot of space in the feed.
Incidentally, nice to meet you all. I hope I can be of some help with the project.