I think most applications just don't care, but when validating it would be nice to follow the standard.
The last comma should also be removed
I think it would be nice with some test with pbn-> lin -> pbn and lin -> pgn -> lin as we should not lose any information during these transformations. But be aware that most implementations of lin and pbn-files are different, so you should select the files for testing, and not assume it would be working on any file.
When dumping a lin file the order of the cards are reversed
I think most applications just don't care, but when validating it would be nice to follow the standard.
The last comma should also be removed
I think it would be nice with some test with pbn-> lin -> pbn and lin -> pgn -> lin as we should not lose any information during these transformations. But be aware that most implementations of lin and pbn-files are different, so you should select the files for testing, and not assume it would be working on any file.