All the cool kids have moved on to adding links to lengthen their comments:
But if you really don't like the punctuation option, get a space from the unicode set and use it:
You should be able to copy and paste that.
mmyers points out that the zero width space is still usable as long as you have characters on either end (ie, it's trimmed if it appears at the beginning or end of the string):
Should work and should be copyable (15 zero blank spaces between the E and the x).
Unless they play whack a mole with the hundreds of space characters in unicode, we'll probably be able to find something that will work as time goes on.
As Grace Note correctly points out, you have no control over the character set viewers are using, so what may look like a space to you may appear to be some odd character to them.
Probably best to link your punctuation - it's unobtrusive enough and it won't break later as they remove other methods of doing this.