I'm not sure about this change. Isn't the point of the ACS_* characters that terminal emulators are allowed to draw actual lines rather than characters? So using normal characters for the corners might end up with a weird, continuous line, bit of whitespace around a corner character that doesn't necessarily match the line thickness, etc., no?

You could refactor it into a separate module if you want.

Another option for the setting is we could add a list as the value of draw_borders, boolean values would have the same behavior as now but passing a list would have Ranger use those characters for the corners (probably best to include all the possible line drawing characters, vertical, horizontal, crossing, various T crossings).