KOReader is so much better, including in how it renders typography and does typesetting than what ships on Kobo devices by default, it's sort of wild.
I actually made a mod to try to upgrade Kobo's built-in reader so it's more correct, i.e. more faithful to how KOReader renders text. Sharing it here since it may be interesting for anyone with Kobo e-readers: https://github.com/nicoverbruggen/NickelTypeFix