Several months ago, I read somewhere (I wish I remembered where) that when one prefaces a statement of opinion with a qualifying statement meant to dissuade the listener from developing a poor view of the speaker in light of the opinion about to be uttered, it actually has the opposite effect.
That didn't make sense, so I'll just explain it by example. If you say, "I don't mean to sound like a snob, but really? You shop at JCPenney?" what you are doing is actually preparing the listener to think that you ARE a snob. "I don't mean to be rude, but..." ensures that the listener WILL think that you are being rude.
This idea tumbled around my brain for a few months, and I wondered if it might be used the other way around. Like, "I don't mean to sound humble, but it was really all Susan's idea." Or, "I don't mean to be beautiful, but this dress looks great on me!"
I posed this hypothesis to Shaun. The example he thought of was, "I don't mean to sound like an expert, but...." I thought that was a really good one, i.e. one that doesn't sound completely ridiculous out loud.
Any other plausible examples?