Characters for diagonal lines
Solution 1:
Slash (ASCII code 47) and Backslash (ASCII code 92)
Solution 2:
These work on my browser, but the displayed glyph width depends on the font, not the Unicode code point. In a proportional font, ASCII i is narrower than ASCII M (iMiMiM).
Below is displayed on a proportional font and are very wide on my browser:
╱ U+2571 BOX DRAWINGS LIGHT DIAGONAL UPPER RIGHT TO LOWER LEFT
╲ U+2572 BOX DRAWINGS LIGHT DIAGONAL UPPER LEFT TO LOWER RIGHT
But a fixed font they are the same as ASCII on my browser:
╱ U+2571 BOX DRAWINGS LIGHT DIAGONAL UPPER RIGHT TO LOWER LEFT
╲ U+2572 BOX DRAWINGS LIGHT DIAGONAL UPPER LEFT TO LOWER RIGHT
Python example:
>>> print('\u2571\u2572'*5);print('ABCDEabcde')
╱╲╱╲╱╲╱╲╱╲
ABCDEabcde