I noticed that Russians sometimes incorrectly spell жирный as жырный, even despite that the rule "spell жи and ши with и" is one of the most basic Russian orthography rules. I also see that Google gives a large heap of results for жырный.
Apparently it is often an intent rather than ignorance, as people often make the letter ы capital:
Хороший официант, прохладная веранда, остальное - жЫрный минус! (Source)
Нашу сеть муж назвал просто «Коля, купи свой Wi-Fi». Это был жЫрный намек соседу — другу детства и редкому халявщику. (Source)
Why do Russians sometimes spell жирный as жырный? In particular, I am curious what they mean to say by that, what the underlying logic of the meaning change is, and how the letter ы changes the pronunciation of this word.