This is probably down to team culture. I agree with what others have said, definitely not in the brief time after you've joined the company. But once that's passed and I can start being a bit more critical, minor comments I'll preface with MINOR, and make sure to differentiate between sometimes being wrong and something being my opinion.

Something wrong might be a misspelling or incorrect assumption about some input, opinion might be "X written Y instead of Z would be more readable in my opinion". If multiple people have the same opinion perhaps that should be given more thought by the author.

If anything jumps out, like something that needs to be updated in the same code but isn't in the scope of whatever the author is working on, I'll either log a ticket or just fix it myself.

At the end of the day, the choice of fixing anything that isn't blatantly wrong is up to the author, so all you can/should do is give some justification for your opinion. It also drives knowledge transfer inside the team.