Aren't those non-ASCII "rich" symbols from Japanese fonts around PC-98/Win95 domains anyway? For me with my background, it was always obvious that mixing full-width character in ASCII text never go well for various reasons. For ASCII arts, it is obvious that vertical lines never line up, and there are going to be tons of wasted spaces and different kinds of whitespaces needed to compensate for those. I wonder if specifying MS Gothic and retuning widths for it could help, at least for Windows/Linux.
Funny you'd mention MS Gothic (fixed-width), since old school Japanese ASCII-art on image boards assume MS PGothic (proportional!) instead. Some sites even try to detect ASCII art and force font-family on that specific post.