After adding MS-DOS and Amiga font rendering for .nfo files, result files and BBS text ads over the last few days, I felt nerd-sniped enough to go all the way and implement full ANSI art rendering.
A few nice examples I found from some brief clicking around...
https://demozoo.org/bbs/185/text_ad/3941/
https://demozoo.org/bbs/5774/text_ad/2689/
https://demozoo.org/bbs/5516/text_ad/2359/
Most of the ANSIs in our collection are BBS text ads, but if you happen to find a production info file or party results in ANSI format, those should be rendered in their full 16-colour glory too...
The code behind this has now been released as a standalone Python library, ansipants https://github.com/demozoo/ansipants - so if you have a burning need to convert ANSI art to HTML somewhere else, give it a go. It's been put together over a couple of evenings, and there are surely quirks of the ANSI format that I've overlooked, so if you spot anything that isn't rendering quite right, bug reports are welcome.