I am not a lawyer but this line of thinking does not make sense to me. First, poster did not post any personal information. Second, the poster responsibly disclosed the bug to Alaska Airlines but Alaska did not fix it. The poster is now publicly disclosing that the bug exists. Note that the poster did not include repo steps for the bug.

The bottom line is we need a mechanism to ensure security bugs are fixed. Publicly disclosing security bugs when an organization does not fix the bug is a good way to do this.

Note this practice started in the 1980s or early 1990s because software venders refused to fix security bugs. The full disclosure movement was created because security researchers wanted the bugs fix and publicly disclosing them was the only way to get some organizations to fix their security bugs.