Comment 3 for bug 166298

Strange, the implementation notes aren't in line with the specs:
* If 'stroke-linecap' is set to butt and the given path
segment has zero length, do not draw the linecap for that
segment; however, do draw the linecap for zero-length path
segments when 'stroke-linecap' is set to either round or
square. (This allows round and square dots to be drawn on
the canvas.)

http://www.w3.org/TR/SVG11/implnote.html#PathElementImplementationNotes

but for a square dot the orientation is unknown so i think
the specs are better. But horizontal square dots can also be
usable of course.

ps I mailed Dean Jackson about it