Top one is actually quite good. If it were for real, I would write it as a proper named function. That way is real nice for avoiding duplication, and something I didn't think of.

def is_palindrome(s: str):
    processed_text = ''.join(c for c in s.upper() is c.isalpha())
    return (lambda x: x == x[::-1])(processed_text)

100% cursed. Love it.

What? Well, yes, that's true, but I didn't write this one. Just pointed out that shortcoming.

You have to add test cases

24 characters shorter, and I respected proper formatting rules (still a joke solution though).

a = [...blaze_it()].at(-1)

var a = 10

lololol

nice!

Better than my own, very good

This works. Better to save the computation to a variable so you don't have to perform it twice. You can do this without regular expressions as well, which (in this simple case) is probably better.

tbh it looks mid

Not quite - "A man, a plan, a canal, Panama" won't work with this method. "racecar" will work as long as it isn't capitalized. It will need to ignore spaces, punctuation, and capitalization.