I've looked at different troubleshooting sites but have come up empty handed. I would say about 25% of my peppers have them.

They start out as a small spot no larger than a dime that appears to have "dried out", it is thin and leathery, but still green (although darker green due to the dull texture rather than shiny surface). Some of the spots eventually turn brown but they really don't spread out at all (or at least not very fast).

I know this is probably a newb thing, but I've never seen this problem in peppers until my Anchos started showing it.

Does it look like any of these?

I had the same thing happen on a few of my pepper plants(various species) when i started putting them out to harden in the sun.  I just figured it was due to sudden exposure to the hot sun.  A few leaves have stayed that way the last couple weeks, a couple leaves dried out and died, but the plants survived and have kept on growing.  Who knows if I'm right but when I started monitoring their slow introduction to the sun I noticed the problem stopped happening.

Sort of... they look similar, but they don't turn brown unless it's a really severe case. Otherwise they just stay a dark green. And they're irregularly shaped, most of those seem very close to round.