User defined tags. The names <user1>, <user2>, ..., <userN> are their default names and they can be changed by a user. These tags are top-level tags in an XML comment and they cannot be nested inside other tags. You can create your own topic sections with them. They can be used for any purpose and their syntax and usage is the same as e.g. <remarks> tag. You can define unlimited number of such tags.
User defined fields have the same format as Remarks and by default they are shown at the end of topic under Remarks. If they are used and you want them appear on some other place, you need to edit output templates. Additionally, you can predefine a default text for each user tag. This text will be used when you place an empty user tag in the comment.
User has defined one tag as copyright and one tag as todo.