Comment by caconym_

There are well established legal standards for what is copyrightable and I believe written literary criticism trivially qualifies (as it should). Stuff you yell at the supermarket doesn't, IIUC, as it isn't fixed in a tangible form. Social media comments are, IIUC, generally protected. The exception would be comments that don't meet the bar to be considered "original", "creative", etc.

(not a lawyer)