This issue is related to the call for style overhaul proposals.

My understanding of how line-art markers get drawn (e.g. "x") is that the width of the line reads from themarkeredgewidth parameter.

This means that whenmarkeredgewidth is 0, line art markers are invisible. This is particularly a problem for seaborn (wheremarkeredgewidth is 0 by default), but I think one could argue that it is not ideal in any case.

IMO, it would be better to have some differentiation between the width of the edge around a solid marker, which is purely aesthetic, and the weight of the line that is used to draw a line-art marker, which isn't. This distinction already exists a little bit in that line-art markers are colored with thecolor parameter and not themarkeredgecolor parameter (though specifying the latter does appear to override the former). So I would propose one of two things: 1) adding alines.lineartwidth (or something) parameter to allow separate specification of the line-art marker width, or 2) reading fromlines.linewidth instead oflines.markeredgewidth.

A related (but possibly separate; I can make a new issue) point is that it would be nice to have some "hollow" markers, like a hollow "o" or "s" which are really line-art markers with the same basic shape as a circle or square, but without a fill and where the line color is derived fromcolor and notmarkeredgecolor. It's possible to draw one of these currently, but you have to do something likeplt.plot(x, y, "o", markeredgewidth=1, markerfacecolor="none", markeredgecolor="b"). This means it is hard to use this style of marker through an abstract interface (i.e. seaborn), which is a shame because this can be a very useful way to draw scatterplot points.