@Jo @lmorchard Not sure "mono"space is actually a thing?
On desktop firefox I get the table not lining up, seemingly because "✔" takes up two columns.
Terminals here would do the "east asian width" thing that would, even in a "mono"space context, make some glyphs two columns wide. Not sure if browsers do that as well?
(ask me about width calculations in a terminal context if you dare)