The font is EB Garamond. It's the only free font I found with historical alternates. At first sight I do think the font should be smart enough to apply those rules for me (contextual features I think, like in "frac"), but it seems, at least on CSS, one must do it themselves.
I'll fix this :D
Truth is, the font does have support for "ſs", and is listed under "Historical Ligatures (hlig)". However, it is only available when "Historical Forms" is turned off. When the latter is enabled, it becomes "ſſ" and I can't find "ſs" anymore (unless manually typing it out).
I think I can learn more by asking at the EB Garamond repo :D
If you happen to know a font that have historical forms support, please tell me. I can't find one beside EB Garamond (I also know Warnock but it's too expensive for me)
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Update: yes EB Garamond does warn this feature is not as clever as the rules on wikipedia. Maybe for now I would choose a safer text for demo while looking for a better font
Turn out it's called "rand" in the spec, but not many applications support that (including browser) so they implemented it via "calt"
#todayilearn