No, prefer to use more lightweight software. Outside of Traktor, I use Mp3tag and Media Player Classic to play/manage my collection. (Around the house I use Logitech Media Server to make the music accessible in different rooms and on different devices.)
I haven't found this to be the case. You just need to do "Check Consistency" in Traktor, either on the whole collection or on the individual files. This will sync the tag data.
I don't think the extra Traktor info is stored in the collection.nml file by the way. I think it's also stored in the ID3 tag, in the private subdirectory under tag "TRAKTOR4". It's binary format, not very intelligible.
The only time I've had a problem with external ID3 tag changes not syncing back into Traktor is when you set a tag to empty, then Traktor will always prefer the previous value stored in the private tag. To get round this you have to "Delete from Collection" in Traktor, choosing option "additionally remove Traktor tags". Then when you next Import Music Folders it will reload the track, using only the standard ID3 tag data.
are NOT converted to 1 Star. Can the value expression be corrected?
However I found some other, old %popularimeter% values from other players in the past:
Easy CD-DA Extractor|255
So my questions: Can the "repeat()" value be more general and cover all possible player/software labels?
As you can see in my "Easy CD-DA Extractor" sample above the original value lacks of the second vertical line and the third value. Could this have a negative impact on the repeat() expression and star calculation?
I am not sure about that.
I take that you have seen in the linked article
"The frame is called POPM and Windows Explorer, Windows Media Player, Winamp, foobar2000, MediaMonkey, and other software all map roughly the same ranges of 0–255 to a 0–5 stars value for display."
And MP3tag shows you much better than any of the mentioned programs the true contents of POPM - I have never seen the values for email or play count (which are also part of the correct POPM syntax) in the named programs.
Please note that MP3tag allows to input ratings as stars, single digit numbers or in the raw format.