Repeaters' bottoms don't render through barriers. See images. One shows repeaters' bottoms with the barrier "no" symbol showing, the other shows the same place with the barrier invisible.
Likewise, redstone doesn't show through barriers from the bottom. See images. I didn't include one of the barrier "no" symbol this time. (Look toward the top, a little to the left; you can see the redstone particle effect from its being on, but the redstone itself doesn't render from this angle.