i would challenge the “unicode is not usually needed” assumption. Unless you have complete confidence in your knowledge of the cultural context of your audience, Latin-1 is a poor assumption. And in an Elixir context, the String.t type is unicode so its not surprising that developers are caught out by the default behaviour of Regex being Latin-1 (even though I understand why the choice, I think its hard to justify as the default).
Latin-1 doesn’t even include the Euro symbol. @michalmuskala’s native language can’t be represented in Latin-1 (Polish is Latin-2). And given the global participation of this forum I’d warrant there are many members building applications for a global audience and therefore should not make limited assumptions on character input or output.
I suppose I may be an outlier on this (Australian, living in Singapore, and having worked in several Asian countries for quite a while). It even bugs me that we don’t consistently address José with the name his mother gave him 
Elixir is a Unicode-centric language. I think that the :re option "u" should be the default.
- wrote a MDSD template generator back then that saved people about 1-2 weeks of typing because they had everything configured (some stuff multiple times)
- but that’s just my opinion.