Comment by biztos

Interesting. Thai characters can also blow it out, I imagine because of the difficulty mapping glyphs to width:

https://biztos.com/hey/thai-mermaid-chart.png

To my surprise, Sublime Text gets it almost right:

https://biztos.com/hey/sublime-thai-mermaid.png

I tried finding a Thai monospace font and using that in the HTML but it was worse, probably didn't have the box drawing chars.

Still a fun tool and useful for lots of ASCII cases!