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There's actually an option in the profile settings to hide signatures if a user doesn’t want them showing up while browsing the forum. Just a quick bit of exploring, and you can get it done in seconds. It’s true that gambling signatures are everywhere since most active posters are in signature campaigns right now, so if it bothers you, hiding them might be the best option.
Of course - it is the best option for those who are bothered by the display of the signature, but they can also hide the avatar. This option will hide the avatar and signature from all other users regardless of what signature and avatar are used - so this is a great advice for those who are not comfortable with signature and avatar.
If they are interested - then they can activate it here: Look and Layout Preferences