Having used a friend's computer with dial-up I know how extremely boring it is without signatures - and how extremely slow and bothersome it is to browse with signatures.
In my opinion, it is common courtesy to reduce your signature as much as possible. Not everyone has a DSL or a huge 20" monitor to view forums with.
You can still make a decent signature at a reasonable file/pixel size.
I also believe this to be true for posting photos. There are MANY free programs that can be used to resize photos. Heck, even those with microsoft have a free one - paint! There are also many sites that can be used to resize once they are loaded (photobucket, zoto, imagestation to name a few.)
I don't seem to have much say on this forum but, I don't think it was right for a moderator to change personal settings, either. They are here to moderate. I can see if if it was days after and messages were sent via-PM or e-mail for a member to change their settings. That said, I didn't see the image that was posted. I'd feel incredibly violated if someone changed my settings in my profile or logged onto an account of mine. Of course, I guess I have no way of controlling or knowing if that happened.
This is just my opinion of course, and like I said I don't seem to have much of a say or ability to speak in this forum.... and my opinion doesn't mean a free chance to bash me.