n e r d e s s a y
There is nothing inherently overpowered about wallbugs in comp play. As laz put it, they're functionally just hiding spots in unconventional areas. On paper, as long as more people become aware of them, they'll stop being nearly as effective. It's hard to be unbiased in saying they're too strong when literally only a handful of people even attempt them, so practically nobody ever checks. And just like normal hiding spots, not checking can cost you a lot.
The main practical difference is that wallbugs are way up high in the skybox usually. While it makes these spots harder to check, soldier doesn't really have any good ways to abuse this position aside from falling down right on top of someone. And most of the good wallbugs are in the skybox where there are no walls to shoot--any lower and they're easy to spot--so soldiers jumping off the wall is rarely an issue.
The only issue here is that all of the wallbugs on the currently played 6s maps are entirely unintentional. What that means is that no thought has gone into balancing them. So while having a wallbug over 1 or 2 chokes on a map is probably fine for a gimmick play here and there, if there is a wallbug over every other choke on the map, things get out of hand.
While hiding spots aren't broken, they're annoying to check and they slow the game down. They're good for the occasional upset play, but they shouldn't be common. The fact that each map has like at least 5 different wallbugs, and a lot of them over chokes and forward spawns, is concerning (especially the forward spawn ones).
But there's really no way to tell right now. On the one hand, people could just learn where the common wallbug spots are and that might make them bad and gimmicky. On the other hand, maybe there are too many good wallbug spots on each map such that it becomes really annoying/difficult to check each one no matter where you push from.
If it ends up being the case that some wallbugs guarantee a kill here and there, then they should be banned. Otherwise, they're just a gimmick and should stay unbanned. Until more people start testing these spots, I think it's too tough to call.