If a user, who has selected "HTML" as the default format for trackers' text fields in "My Account", creates a new artifact, the "Original Submission" field is in "HTML" format (OK). If the user changes the format to "Text", and writes some contents in the field before clicking on "Submit", the artifact is created and its format is "Text" (OK). Now, if the user changes the contents (not the format) of the field via the REST API, the contents is modified and the format is set to "HTML".