Separation between anchor links?

I have a distinct recollection of having seen a recommendation to
always separate anchor links by at least one non-whitespace character.  
This was probably in an earlier guideline document, maybe at CAST or
WGBH.  Wherever it was, I found it eminently plausible, and it
convinced me at that time to redesign my navigation "bar" (actually a
row of button images).  I decided to separate the buttons by 1-pixel
transparent gifs that have their ALT text set to " | " (space,
vertical bar, space), so that they're practically invisible on a
graphical browser, but show up clearly, between the anchor links, on a
text-mode browser.

The issue came up again today, and it occurred to me to look for some
advice on this point in the WAI guidelines.  But I didn't seem to find
anything specific.

Any comments, please?