Beyond just characters, though, a broader base of information better informs what you produce. A lot of the sexism that shows up in mainstream comics, I think, stems from the fact that there are so few women in the industry. Male writers are just writing what they know: men. So female characters come off as shallow or two-dimensional; there's no real reference outside of all the other shallow and two-dimensional female comic characters.
I bring this up, to some degree, in response to Google's changes in their search results, which are now incorporating social media aspects to the top results. Basically, if you haven't seen/experienced this already, the upshot is that anything you search on, the first results are, whenever possible, going to be pulled from your and your friends'/acquaintances' sources. Their Picasa albums, their blogs, their Google+ posts, etc. The potential issue there is that your searches are more narrowly focused on what you and your friends already know. Eli Pariser calls this a "filter bubble."
Personally, I try to actively combat that filter bubble. I still read an inordinate amount of material relating to comics, of course, but I do try to counter that with some other things as well. Right now, I'm reading a biography of Cleopatra for example. I also specifically went in to TURN OFF those personalized search results. I found having those only really distracting because I don't want to search on what I already read through a link on someone else's profile; I want something new!
You can walk around in circles if you like, I suppose, and stay within your comfort zone all the time, but I'd rather see/hear a wider variety of voices than just reflections of my own. I might disagree with many of them or find them wholly irrelevant, but at least I saw that my thinking wasn't the only option out there.