I’m sure there’s some amount of overfill that’s OK, but who knows what it really is?
I am also sure that a competent oil change place can fill a car to the ‘full’ mark and not above.
Running a 1/4" over the full line (or even more) will hurt nothing. A bit of additional oil just aids in the oil cooling and also provides a tad bit of a safety margin in regards to oil consumption, oil slosh in the pan, etc.
Of course there are limits; you do not want to run an additional 3 or 4 quarts as that could possibly cause oil frothing. It would not cause a head gasket failure.
An extra quart, assuming that amount is involved, is harmless.
The same thing applies to transmission fluid. Within reason, it’s an aid rather than a detriment.
Measuring the dipstick only accounts for 1/2 of the potential problem. You would need to verify that the tube is also the correct length since it controls how far the dipstick goes into the crankcase.
1/2" overfilled? Much would depend on the particular design. However, if you turn that around and gauge what the dipstick would read if it was 1/2" below full, where are you in the MIN/MAX range, if at all? If that is below the MIN fill point, then I would be VERY concerned about how 1/2" overfilled translates into potential problems. On most of my rides, 1/2" over the full mark would be a significant amount overfilled. I wouldn’t want to run around like that.
The quick lube places will always get it wrong if their database says 6.1 and it is supposed to take 5. The autofill mechanism will be set to deliver the 6.1 and they are not likely to double check.
“I am also sure that a competent oil change place can fill a car to the ‘full’ mark and not above.”
You are right, of course, but–unfortunately–the OP has chosen to patronize Jiffy Lube, whose name is rarely if ever heard in the same sentence as the word, “competent”. As Joseph Meehan has said, “don’t even go to a quick lube place for directions”!
(Speaking of which…what happened to Mr. Meehan, who has been one of our regular contributors for several years?)