in Australia (and no doubt some other left-driving countries) - everyone stands of the left.
In left-driving London there is a convention on Tube escalators that everyone stands on the right, and lets the walkers go up the left. Anyway, it's simple courtesy in any situation not to block a narrow pavement or walkway by standing or waddling two abreast.
Anyone old enough to remember when riding bikes as kids that we were taught "no riding two abreast on public roads if there is any other traffic about, and no riding three abreast ever" ?