We currently warn on preg_quote() with no second parameter, but this is valid and correct:
This is the modern recommended style for this sort of expression, so the warning is often a false positive; drop it.
The "CLASS" warning looks for hard-coded class names in strings, but currently looks for them as a word anywhere in the string.
This is often a false positive and sometimes makes error messages or exceptions untranslatable. For example, translators can't do anything with this:
Filesystem path "%s" does not exist.
...if it's written as:
%s path "%s" does not exist.
...just because it happens to appear in the class "Filesystem". Some other classes, including "Future", suffer from this.
Even when the detection is correct, it's clunky and a mistake here (failing to update the class name in an error message) is unlikely to ever do any real damage.