I think that either there is inherent magic in some symbols and language or they can be "charged" with spells. I assume that's how scrolls work and I think that robe Elysana enchanted had Daedric text embroidered onto it.
There must be a reason for why the Daedric language is used in magic and it may just be that Chimer and some humans at least learnt a lot of magic from the the daedra. Maybe a lot of destruction as well as conjuration which was taught in both the Mages Guild and the College of Winterhold is derived from witchcraft, even if one doesn't have to serve the daedra in order to use it. I'd be surprised if Altmer used Daedric that much, but then their magic probably dates back to when they had similar ancestor worship beliefs to the Psijic Order when the daedra weren't defined as "not our ancestors". Dawn magic might be a different story.
Don't read too much into the exact text on the runes. Most of the scrolls in Morrowind said "Woe upon you", including healing scrolls and others were http://www.uesp.net/wiki/Morrowind:Scrolls. It doesn't mean that the text isn't supposed to be significant.
In fact why do the daedra have a common alphabet/language?