Any shader can do this if you understand render queues. Poiyomi for example can do this if you set the magnifying glass’s glass to a mode like “transparent”.
If I understand correctly, the trick that the magnifying glass uses has something to do with render queue. If any item on an avatar’s body is set to something like “cutout” or “transparent” in poiyomi per say, then looking through another transparent mesh of the same render queue will render it invisible (as long as it’s not a two-pass shader.) Many people have their clothing set to cutout or transparent for various reasons which causes you to be able to “see through” their clothing because their body shader is set to “opaque”.
I’m pretty bad at explaining. I can reclarify anything that doesn’t make sense.