Rune Chain Spell not working - after selecting friendly troop

[Xargon]

You're right, this spell is great for single-stack damage, I had not realized it before (I looked at lvl1 and the damage did not seem impressive to me, but it scales really well with higher levels).
But it worked as it should for me when I just tested it - first select one or more friendly troops to take runes from, then the enemy. And the damage was correct.

Incidentally, I noticed something else: the [edit: morale bonus from] bloody pentagram from demons does not affect summoned demons (from demonologists and demons themselves), even though they are friendly (but fighting on their own).