I have a custom list on SP Online 2013 with the following customizations:

• Create a version each time you edit an item in this list? - Yes
• A new column added (multi-line) with Append Changes to Existing Text? - Yes
• Allow management of content types - Yes
• Launch form in Dialog - Yes

There are no workflows or anything else.

Whoever is the creator of an item in the list shows up as the modified by no matter what. I've tried this with several users of different access levels.

Any thoughts on what I could try?