Yes, you're right...
I checked the url you posted, and found that they're using a plugin for image filtering... this plugin adds some custom functions to the image url...
That's why IPS strip the customization added to the url...
As an action, I'd add check function for customization in the url, if found and the user don't have permission to post html the image should be stripped.
That was intended to keep the style intact... but as per your suggestion, I'll add it as an option in plugin settings.
This one also will be considered in the upcoming version.
Now this request is doubled (You're the second one to request this option).
I'll think about it and check what can be done.