On my tweaked Firefox profile, _⎽⎼—⎻⎺‾ renders as 3 different fonts (Courier New, IBM Plex Mono (my monospace font), and Segoe UI Symbol), with different widths and heights, some of which aren't even monospace. On a clean profile, it's only Courier New and Segoe UI Symbol. In both Firefox profiles, ⎺ renders higher than ‾ despite coming before it in order.
It might work on certain fonts and terminals. It's not a general solution for blogs IMO. Are we better off with terminals with first-class support for sub-cell graphics rather than text, considering people tend to hack in graphics in terminals (the various htop replacements with terminal graphs, and this)?