This was originally noticed and fixed back around the beginning of July. As of August 1, this problem seems to have returned.
New bug report is here: Single site SE flair not displaying the correct icon
I just happened to notice that my SO flair has some sort of a
B icon right before my username (instead of the expected site icon)
Snapshot of the unknown icon:
My current (live) flair for monitoring:
It currently showing up like this for all users on all sites, but not on Combined or Meta flairs. For example Jon Skeet flair on programmers: