I find those quite odd. It seems overly ornate compared to the rest of the font, which doesn't even contain the 'fi' ligature.

Me too, this is the Linux Libertine font. I need to fine a way to disable those ligatures :)

Please, all deities, nobody use that ST ligature. It's cute for about a millisecond and then it's annoying.

I checked just now and indeed that ligature has been supressed in the recent versions of TeXmacs. :)

It was never the default. You don't get them unless you specifically ask for them.

No,in a previous version of TeXmacs they were active by default, we changed that now.

It is not Linux Libertine, it is Biolinum, which happens to come packaged with Libertine. Libertine is a serif font in the Caslon penumbra.

The author turned on the "st" elective ligature, but not the "ct", which is entirely why it looks odd.

You don't get those ligatures without specifically asking for them. It must be said that the Libertine ones look better.

Seriously, is this really a (good) thing? I opened the slides, and spent the first 3-5 seconds having my eyes drawn to this ligature, trying to figure out why this word is different than what my brain is used to. I cannot imagine that this is a desirable effect.

Clearly, I'm missing something, happy to be corrected!