I will agree that the elixir regexes should include the u flag by default and require explicit opt-out. We generally should prefer correctness over speed with ways to opt-in into faster, but potentially incorrect results.
Unfortunately, the soonest we could be able to change this would be 2.0 (and there are no plans for 2.0 at the moment). This is because that would be a breaking change since many functions would start returning different results.
