In perusing the release notes for Subtext 1.9.5, I noticed that Subtext now implements "Identicons". "Eh?" sez I. Not that I don't know what identicons are. They're a way to encode a web address in a manner that makes each address graphically unique with related addresses adopting a similar look.
Reading Phil's post, you can see identicons at work in the comments along with Gravatars (which Subtext has had for a while now—they're a central repository of an image representing you based on the email address associated with the post). Now, I've been meaning to implement gravatars in my Subtext skins for a while now, so I figured now seemed like a good time and began poking around.
Ouch. The original skin I copied six months or so ago didn't have gravatars in it, so I picked the code apart a little to figure out what might be needed. It turns out to be pretty easy, even if it took me forever to find: just add an asp:image with a particular id attribute to your Comments.ascx control. Subtext's default skins (I have got to start looking there first for these things) have it already.
Only, that turns out to be the easy part. The tricky part is figuring out that you'll also need to edit the web.config. Gravatars are documented on Subtext's main site, but it's a touch out of date, so you need to make sure that you have an updated web.config. Which is just as well because identicons are even newer and they're not documented at all except in the web.config file. The gravatar section looks like this:
Making sure that "GravatarEnabled" is set to true is the first bit, but the key to identicons is buried in the last four lines. Essentially, all you need to do is change them to look so:
With this, you're golden. Any gravatar that comes back empty gets made into an identicon. It does this by sending gravatar.com the identicon handler address in place of the "{1}" in the "GravatarEmailFormat" setting.
The only tricky part from there is updating the skin and appropriate style sheet(s).
UPDATE: After playing with issues of the above code displaying poorly on my current skin, I've swapped the <pre> tags out for images. I just didn't like where it was going with the clipping vs. scrolling and all. Clicking either image will give you a page with the original text (in case you want to copy and paste or just for nostalgia's sake). Apologies for anyone who was trying to read the post while I was futzing.