Yes, I've encountered them. It seems really hard to do them in a way that doesn't touch heavily on style. To the extent that the preferred solution to trying to shift the focus back to deeper issues is to go one step further and mandate auto-formatting tools. So individuality-of-style has been dismissed out of hand.
Can they be helpful? In some cases, perhaps yes. But they're definitely pushing a collective-ownership, try-to-smooth-away-individual-differences agenda.
It is much easier to read code that is written consistently, and it's much easier to contribute to code when a style guide is available. This isn't "pushing an agenda". And what's wrong with collective ownership?
Code review shouldn't involve bikeshedding about whether braces should go on the next line or not. It should be about design decisions, clarity of expression, algorithm complexity, etc.
Other users have already described healthy code review processes that improve code quality while helping all participants to grow individually and as a team.
How does review treat programmers like cogs in a machine?