You're making an excellent point: the behavior of this normalizer regarding tabs & newlines isn't specified (only tested with normal spaces in specs), nor clearly documented:
> * _:squish_ Will strip leading and trailing whitespace and convert any consecutive spaces to one space each

I was personally using this normalizer on `varchar` columns (usually represented with a simple `<input>` field, thus not really facing the tab/newline problem), but as soon as I went using it on `text` columns (with `<textarea>`s), I realized it was dropping newlines, a behavior that didn't suit my needs (basic `simple_format`), and that I personally found surprising, and deceptive according to the documentation.

IMHO, either the documentation & specs have to be updated accordingly (which makes this normalizer almost useless for multilines attributes), or the implementation has to be modified to follow the documentation (which will not be backward compatible).

BTW, maybe another normalizer could be introduced for multiline attributes, to remove all control characters except for newlines:

```ruby
config.normalizers[:remove_control_characters] = lambda do |value, options|
  value.try(:gsub, /[[:cntrl:]&&[^\n]]/, '')
end
```

Anyway, I'd be happy to help :)