You are correct about how ankh runes work. It does indeed stop me from
using malloran, as well as my opponent, if I just let it sit there. However,
I'm a bit more clever then that, so when I use ankh runes, I can still
make use of malloran, but my opponent can't. I find thise quite useful.
As for diffusion, why not use a pyramid rune as well if you're worried
about being summoned?
Written by my hand on the 27th of Paglost, in the year 999.