I have an exporter attached to a pattern grid that exports blank patterns into the input slot. I also have a pipe that pulls out the written patterns (blacklists blank patterns) and routes them into a bunch of crafters. This way I don't have to carry the written patterns and put them into the crafters manually.

What actually happens is 64 blank patterns go into the input slot and 1 blank pattern goes into the output slot. I'm expecting not to be able to pipe into the output slot. Note that this doesn't break the setup, but it's just a bit weird overwriting the blank pattern.

It seems this could be fixed by disallowing blank patterns in the output slot. You shouldn't need to put them in the output slot anyway, since you might as well just put it into the input where they will stack.

Minecraft: 1.2.12
Forge: ToT
Refined Storage: 1.5.34