*Commentators explaining endlessly that "this scene was filmed in two different places and times!" Or,"This is a set doubling for a real room!" Or,"We filmed these scenes out of order!" As though these filmmaking practices are still novel after all these years of DVD commentaries pointing them out.
*Commentators dutifully pointing out that the film's female lead is "not only lovely but also an excellent actress!" Also in this category is when the actress does a nude scene and the director praises her professionalism and commitment more vigorously than ever, as if to compensate for making her provide fan-service. "It was so cold that day, too. She's such a trooper! Such devotion to the craft."
*Directors of an indy film or comedy enthusing endlessly about "how lucky we were to get (some Oscar-winner who is slumming in their film) to do this part!" And on and on about how they worshipped him/her on the set, and how much they learned from him/her, and what richness s/he brought to the role, even if the Great Actor only had a small part and delivered an unremarkable performance. Also in this category: "I didn't dare direct him! I just got out of his way and watched him make magic!" Ick.
*Hints about comments that will come later. "There's a great story attached to this location that I won't tell you now, but later when this location crops up again I'll go into it in more detail." Thanks for warning me; I'll sleep more easily. Also: "I don't want to give away the ending, so I'll keep my mouth shut during this part. Well, maybe I'll give a few things away. Do you think these people have seen the film already? If any of you haven't seen the film, please turn off this commentary and watch the film first...." How many times do I have to hear that speech? What planet are these people on?
*"Did you see that guy in the crowd, in the green shirt? That was the set dresser's brother. Yeah, no lie! He was just visiting the set and we put him in the shot!!"
*When directors and actors say,"This is the first time I've watched this film since the premier, 15 years ago..." or "I never watch my own work." As if the film itself is just a trivial by-product of all that fun they had on the set. How do they expect to improve without periodic self-examination? I can't imagine a chef saying,"I never eat my own meals."
*When the director can't recall someone's name. "That actress did a great job. I don't remember who she was, but she was great." Especially bad when they're talking about a crew member or stunt person, whose face doesn't appear on camera. "Great stunts/set design/singing by what's-her-name." Her moment in the sun, ruined. Go to IMDB, fools, print a list, and have it in front of you as you comment!
*When they comment by merely describing what's happening on the screen. David Mamet and Mel Brooks are awful in this regard.
Brooks: "This next scene is really funny. Dark Helmet comes on, and he's just this short guy with a giant helmet. Cracks me up!"
Mamet: "This girl who played the stripper? Great body........yup. Very fit."
Do they think commentaries exist as an aid for the blind?