Now that we're mostly writing novels, that rule has largely fallen by the wayside. Still, we do keep a check on each other to keep up on what everyone's doing. Practice, practice, practice. You won't get better if you're not producing words on the page. When a work is being critiqued, it is the work that is being critiqued, not the writer.
Personal comments are a no-no.
A critique is personal enough, it should not be an attack. Take the criticism, weigh it and see how it feels to you, then take it or discard it. If something only bothered one person, it's probably okay. If two or more people noticed a problem, you'd probably better think seriously about changing something. If everyone had the same problem, you'd better make sure you change it.