Flagged by @dadoonet in Slack:

> Hey team. There's an interesting discussion on discuss about Lucene regex support.
Our documentation says things like:
[a-c]   # matches 'a', 'b', or 'c'
[^a-c]  # matches any character except 'a', 'b', or 'c'
Which is correct unless you use as well case_insensitive: true option. In which case you would expect B to match [a-c]. But it does not work that way and it's a known limitation as Robert answered in apache/lucene#14378 (comment).
Could we document that somehow?