The icon filename should not end in any of the following five letters: A, L, M, S, and X. (Neither upper-case nor lower-case are allowed.) These are reserved letters used internally for icon sizing. Unexpected icon placement results may occur if your icon filename ends in any of these letters
is this "feature" obsolet in 10g? I think so. The only point is, that the online help isn't actualized ?
That "feature' *is* obsolete, if you noticed the online help still talks about .ico files and not .gif or .png.
Moreover I have tons of icons that ends with the letter N and S both in lowercase and uppercase, so my guess is that the online help was not updated properly.