On the one hand it's their posts and nobody can tell them what to do with them, though downvoting/flagging is always an option.

On the other I can see that it's already become a link spamming endeavor and the logical conclusion is a bunch of low value comments everywhere with loud and spammy images linking to anything but something relevant. The Bitcointalk forums are a perfect example of this.

Thanks for bringing this up, I think low value comments with these loud signatures should be discouraged with downvotes. Discretion should be used if the comment is worthwhile and on topic though. 

For instance, it looks like @bravenewcoin's comments are high value and on topic, although I find the image to be pretty big compared to the size of the text. I hope some reasonable balance can be achieved.