A recent discussion here reminded me of this, which I noticed when I first tried MC, several years ago. I reported it at the time, but nothing has changed since then.
MC will alter the tags of certain flac files when it imports them, even if tagging is turned off. So far, I have seen this happen only on files that were tagged with the GoldWave audio editing program. Perhaps it produces tags in a nonstandard format; I do not know. They seem to be readable by other programs.
Want to see this for yourself? Here is a sample file:
http://www.storebrandchristmas.org/sbc/misc/files/Silence5.flacThis a simple file containing 5 seconds of silence, created and tagged in GoldWave. It is 793 bytes in size. Once downloaded, note the file size and date/time stamp. Now, run MC17, and make sure tagging is disabled. Import the file into MC, and then check the file size and date/time stamp again. The file size increases to 5k bytes, and the date/time stamp is updated.
Should this be happening? Especially when tagging is disabled?