There's been times where it's the right thing to get involved, and other times when it's not. For example, we had an issue with full ticket completion: sometimes 3 of 5 requirements would get complete, and then the work was merged. I wouldn't review line-by-line, but I would cross-check the features and note if I found something missing. To be clear, I would not dictate how to do the work. In the meantime, we instituted processes to ensure work was completed in full, and once the team norm'ed around the new process, I stepped back.