Not everyone uses Xcode as an editor, some actually like things like emacs, vi, bbedit, etc these are usually aware of the standard unix comment character for single line, #
I typically have a line starting line 1, column 1, like
Vim and emacs bothsupport C style comments just fine. I don't think ease of copy/pasting these comments from non-C style languages is important enough to introduce a weirdly-behaving new comment character.
You might very strongly believe that this should be supported, but your response is inappropriate. You're suggesting making a change to the language which might have far-reaching consequences; if you want to convince others that this change is worth making, you might want to consider the tone and words you use to do so. Personal attacks are not going to get you what you want.
From a technical/process perspective: many languages don't support # as a comment character, whether at the start of a file or not. Adding this to Swift at this point would likely require the feature to meet a pretty high bar, which I'm not sure it does. Adding # for the benefit of a shebang line, perhaps — but add this to support a handful of specific text editors (which support regular // just fine for the same benefit), less likely.