Today I used the bottom of my T-shirt to gently wipe some stubborn dust of the front element of my lens (i.e. I took the filter off and cleaned the lens itself). Quite by chance I've stumbled upon a post on a web page this evening saying that you should never use anything but an approved lens cloth to clean the front element as alternatives can erode the coating (???). This appears to be a post from a non-pro and I'm suspicious about the reliability of such info; but another part of me is suddenly worried as, although I don't make a habit of it, I have done this before.
Is it nonsense do you think? I would be inclined to say yes but I'm really not sure. My lens is the Canon EF70-200 F4 L by the way.