Line filter: Should case insensitive be the default?

[gtk-grafana]

This conversation keeps coming up, creating this issue as a place for people to drop in their ideas and opinions.

Case insensitive by default means slightly worse performance for Loki when adding line filters.
Case sensitive by default means slightly worse UX for users that expect search results to be case insensitive.

I'm leaning towards allowing admins to configure the default, so large at scale loki instances get more performant queries by default at the expense of a slightly more complicated UX.