Am I overreacting? How to handle PR comments

I believe a good code should pay attention to the existing coding style of the package or library or team that you are changing to minimize confusion for the next person.I would strive to document this coding style to make it universal. Ie, point them out to the coding style guide that your team is using.Arguing over coding style without setting standard is pointless.

Just ignore the comments and merge if its approved

Is the preferred coding style is documented? If yes, please follow it, else ask him to document and then follow it

Code review is the most $hitty thing to do. Everyone is a hero when they become judge

Telling what? Not to review PRs that are accepted?

Just dm him

Better yet, send an email to the team that your team needs to agree on coding style and create a checkstyle or something similar to enforce it at local build time. Document this need and ask this engineer if he can take a stab at it next time he leaves those comments on your code. He gets to create this checkstyle as per his preference and you get the points for driving uniform coding style practices in team. Win win

I work in a place where people don't auto indent code even when using ide's like intellij and mix various coding styles in one method.

It's a horrible thing to do, which shows that people are not showing enough attention to code. I personally can't stand such folks.

I believe in putting your ego down and following the more experienced developers advice. If you think your code style is better please put the reasoning in the pr comment which will speak for itself.

If it's related to code styling/ formating, get a perl script to annoy you instead of him. Harder to get embarrassed by a script running locally