Rotating things via the wand of the forest shift-click functionality causes the wand to change between bind mode and function mode.

I tried, I can't fix this in a way that isn't crazy hacky. Sorry.

Wouldn't returning true if block.rotateBlock (at https://github.com/Vazkii/Botania/blob/master/src/main/java/vazkii/botania/common/item/ItemTwigWand.java#L86) returns true work? Or am I missing something?

Yes. That's what I thought. However, block.rotateBlock returns false on clients every time, which means the right click event gets passed to the server, which changes the wand's mode.