Comment 2 for bug 850258

Hello cosimo, thank you for the screenshot and the bug report.

I've marked this marked this as a dup of bug #788757 ("Mono: Not all box drawing characters are mapped"). What's happening here is that those ASCII box-drawing codepoints in the font are not present, so are getting substituted from other fonts, most likely DejaVu Sans Mono. The substituted glyphs coming in are 600 F-units (600/1000s of an design em square), so overlap with each other.