SUMMARY When adding a comment for a file, the comment will not be recorded if the added text is larger than the file system allocating space for extended attributes. An returned error must be displayed. STEPS TO REPRODUCE Add a big comment for a file (bigger than 4kb for ext4) OBSERVED RESULT Comment seems added, but its not.
By the way, it is unlikely, but any entry in the extended attributes (such as tags or rating) can cause an error if there is not enough space, so any entry should be notified of the error, or carry out a check before an error idk.