The merge operation will combine the information from the source entity into the target entity according to the following rules:
If the target entity has a field set, that field will be preserved.
For checkbox fields, if at least one source entity has it checked, it will be checked in the target entity.
If the target entity has an empty field, but a source entity has that field set, the field will be set for the target entity using the information from the first source entity.
All collections and multi-selects will be merged, with all entities from the source collections moved to the target entity.
Comments will be merged, possibly from a system user.
Highlights will be set for the new target entity.
Content from rich text fields in the source entities will be appended to the target entity's rich text fields, with a prefix H3 header indicating the merge source.