This relies on limited number of precomposed characters and browser fallbacks to a font containing them. Chrome/Windows cannot display anything except first and second-to-last lines, IE and FF work fine though.
You could instead use combining characters (\u20dd, \u20df) to decorate any unicode char, but the number of fonts supporting this feature is extremely limited. One such font is Cambria on Windows, but spaces should be used to properly center a char inside enclosing mark (<char> + space + \u20dd) [1]. I wonder if a font exists which fully supports combining chars and contains metrics for centering them.
You could instead use combining characters (\u20dd, \u20df) to decorate any unicode char, but the number of fonts supporting this feature is extremely limited. One such font is Cambria on Windows, but spaces should be used to properly center a char inside enclosing mark (<char> + space + \u20dd) [1]. I wonder if a font exists which fully supports combining chars and contains metrics for centering them.
[1] http://jsbin.com/cuxogojivo/2/edit?html,css,output