Mary Fisher wrote:

I have a baby pepper!

About an inch diameter, hope it lasts long enough to grow.

I've got a few reasonable sized sweet peppers now. They seem to be
taking forever to turn red though.

I wonder if I should be
thinning them, as with tomatoes?

I'd leave them to their own devices. If they form a lot of fruits and
you want larger ones, you could remove some, but at this time of year
with lots of growing season left until the frosts, I'd leave them to
their own devices.

Peter