I posted the wrong example. Here is the snippet where the problem is created ...
(newFileName & space & suffixNr & ".emlx")
set newFile to my copyFile(sourceFile, dayFolder, the result)
if class of newFile is alias then
set modification date of newFile to modDate -- date sent
set comment of newFile to (mailComt of headerRecord)
end if
The sourceFile has no comment. The newFile's comment is set in the last line.
The comment appears correctly in kMDItemFinderComment,
but the Finder does not display this in a few cases.
Hope this clarifies the problem.