Using the gui action=edit§ion=new without a summary, no == == is generated in the save content.
For the api the module action=edit have a summary and a sectiontitle param. Using a summary and a empty sectiontitle generated a == == with the content of the summary. In my opinion the empty sectiontitle param should suppress == ==, but the summary param should still used for a summary.
When that get fixed, a gadget can still generate non headered section (often a subst template contains the headers), but used the summary to say, that is coming from a gadget.