loftar wrote:Ah no, you misunderstand.

I was not referring to the phrase existing as an idiom in Old English. The context is as follows: I tried to formulate "I have returned" in O.E. and finished with the remark that I couldn't do it idiomatically correctly; then Jackard told that I must; and I tried to respond that I couldn't do it.

I had the smoldering suspicion that that was the case for ために, but I believe myself to have read できる in kanji many times over. Am I just imagining things?
Ah, sorry, my bad. I had just come back from a bar, after all.
You were much closer than I thought at first, actually, but the devil is in the details. It is kind of like the difference between:
"This is dedicated to my parents, Ayn Rand and God." vs. "This is dedicated to my parents, Ayn Rand, and God."
Or
"I walked and talked with him 30 minutes after he died." vs. "I walked and talked with him. Thirty minutes after, he died."
As far as the kanji goes, it is much more of an art than a science, but generally speaking, as the formality increases, the use of kanji for modals and particles also increases. It is hard to explain precisely how to use them correctly, but using 為に, 出来る, and こら together has the issue (very roughly) of the following:
"Ladies and gentlemen, cop a squat."
It is hard to convey the feeling correctly in English, tho.