In the basic editor, it is possible to manually search for an authority record and link to it while preserving the original punctuation in the bibliographic record. It is also possible to search for and link to a broader heading and the additional subfields will remain intact in the bibliographic record. If you try to do either one of these things in the advanced editor using ctrl+shift+L to get to the authority search, once you link to the authority record that you select the MARC field you are editing will be rewritten to match the corresponding field in the authority record. It would be very nice if the advanced cataloging editor would simply append the authid in $9 and leave the rest of the MARC field alone.
Thinking about this one, I am not sure if it always fits expectations. I can see where it's annoying when you have already written up a nice entry. But what if you are working with very minimal records and want to use the more complete information/punctuation from your authority records? Should additional subfields like dates be added that haven't been there before? They would require a change of punctuation too if I am not mistaken. Wondering if we could create a flexible solution that works well in different scenarios, maybe using a dialog or an option in the editor? Also: when an authority main heading is updated, the linked records are changed as well... so there are other workflows that might change your entered heading automatically.