This is true, that is, unless the app utilizes Installer.app (Apple's) and creates a receipt package.Third party installs do not touch system permissions.
I never claimed that system permissions was the source of corrupt plists. However, when backing up to a non-local (external) volume (like a FireWire HD, a USB 2.0 HD, or a disk from FireWire Target Disk Mode) via ditto (with the --rsrcFork option passed) or Carbon Copy Cloner, (one really shouldn't use drag and drop in the finder or cp to backup OS X volumes, as important metadata can get lost that way) there is one reason that the use of ditto or CCC would require a repair permissions on the volume everything is being backup up to--when the volume has the "Ignore ownership on this volume" checkbox checked. Ignore Ownership on this volume should be unchecked - if not, then none of the permissions will be copied over in the first place and then you have to run repair permissions to make the thing bootable. But its still not recommended as any files not installed by the installer won't have the permissions fixed and could potentially create problems.You can quote "many problems" if you wish, but how about naming ONE? Just ONE that has been fixed by running "repair permissions". Because system permissions is NOT the source of corrupt plists.
Actually, repairing permissions did more good for those utilizing Classic OS9 within OS X. Back in the days of 10.1.5, (pre-Jaguar) if you booted into Mac OS 9 and ran some common applications, compressed and decompressed files, moved or renamed files, or (worse) ran a disk utility like Norton, they could completely destroy the permissions for many files that OS X needed to boot or run correctly. This was fixed in after the 10.2 release, mainly because new Macs were unable to boot from OS9.The fact is that people do this "repairing permissions", because they feel the need to perform "maintenance" on their computer. When OS X, because it is in fact a UNIX system does not need it. It maintains itself well enough to not require user "maintenance". It is just something people "miss" from the bad old OS 9 days - like the "Rebuild Desktop" voodoo, or "defragging the disk", both of which had more utility than performing "repair permissions" as maintenance. The latter moreso than the former.
All in all, I agree, permission repair is generally overused and will not remedy most common problems. I will therefore refrain from recommending this in the future.it is a troubleshooting tool, not a maintenance you need to perform like a magic ritual ever so often.