If you have a two block high gap with a repeater on the bottom you are unable to walk through the two-high space unless there is a block two above and one before the block that has the repeater on it. Technically it would be a one-high gap since the repeater is taking up the bottom block but it's inconsistent to have it work this way.
From how redstone dust works I'd assume that being able to "walk through" the repeaters is the correct functionality but I'll let a moderator weigh in.
I've attached a screenshot - you are able to walk through the left hand "door" (with the brick over it) but not the right hand door.
(I tried this with pressure plates, redstone, string, all types of rail, and snow; they all worked as I'd expect)