I notice that when I look at my "Account", under the Preferences, there is a Content Options section. One of the options is "Show people's signatures with their messages". I like seeing what instruments other members have in their collections, so I have this box checked. But, I'm thinking that for those that don't like to continually see people's signatures, they could opt out with this button.
There are also a lot of cool options for receiving alerts about messages a member has posted or is following... or not to, if you choose!