I used to only play third person perspective (old school "regular", aka 3pp) but lately I've made some friends who play first person perspective (old school "hardcore", aka 1pp). People always note how you can exploit 3pp to peer around corners and over fences in a way that's unfair or abusive. However, I discovered that 1pp can be far worse, and maybe this explains why some people play 1pp.

With a weapon drawn and slowing walking forward you can easily view clip through walls and see what's going on in other rooms or even outside of a building. This is far worse than the clipping I was able to test out in 3pp, it's trivial to see through *nearly* any wall.

Screenshots attached.