Yes, and it's proven an awful suggestion; I'm surprised Google was promulgating it. Specs from the 1980s are filled with terrible design choices. Heck, equalp and equal are recommendations of the standard as the only two "structure-equality" options for hash tables -- and both of them are broken.
I disagree that it has "proven an awful suggestion." Proven how? Through what experience? I've found the one-semicolon comment placed at a suitable column (as recommended by the spec) leads to very clear and easy to read code annotations, even without syntax highlighting. Emacs does a fine job managing the formatting of these one-semicolon comments (e.g., setting at the right column, justifying/reflowing the comment over multiple lines, making sure the comment doesn't overflow your preferred source code width), and with syntax highlighting, they're even more patently visually obvious.
You seem to think that the choice is acceptable because "it works fine in Emacs". Language design decisions should not be based on the choice of editor. Indeed Google's own examples are not syntax-highlighted. And offsets won't do the job either: Google also recommends that lines not be longer than 100 characters, which makes it rather hard to guarantee that inline comments be offset by very much.
A single-semicolon comment is intended to be very terse and to-the-point. Longer inline comments are supposed to be double-semicolon dedicated to their own lines.
(let* ((head (cons nil nil))
(tail head))
;; This is a longer expository comment on the following
;; segment of code. Here, we efficiently append to a list by
;; keeping track of the tail node at all times.
(dotimes (i 10) ; RPLACD+SETF is an O(1) append
(rplacd tail (cons i nil))
(setf tail (cdr tail)))
(cdr head)) ; discard dummy cons
I don't think this style of commenting is acceptable because of my editor, but just that an editor like Emacs keeps it very easy to edit, organize, and reflow them. I have no shame in saying that I use my editor as an integral part to my programming workflow. :)
I know this is common. It is also bad. A single semicolon is small and easily visually lost in the visual noise.