For web: better theming, for app: i18n, for both: much smoother subscription to other instances.
IMO there’s no such thing as “on Lemmy” in general, unless you mean this specific instance of Lemmy. But anyway, this problem of balance seems to be an eternal philosophical question which may be never solved once for all. Each instance chooses its own combination of censorship and freedom.
Also, wondering about the following:
I used to hear this joke with a cat or horse instead of duck, being a programmer rather than a roofer. Anyway, funny!