While fixing some test @ MDL-58643, a couple of details were found related with the participants page. Commenting here so they aren't forgotten. Note that the same "problems" happen in previous versions of the page, so this is just something to consider an, if viable, improve:

A) Sorting is not 100% logical/deterministic. When sorting from some "empty" concept (like not set city, or never accessed to course...) results are DB dependent. In fact that was causing MDL-58643 with mysql being ordered 100% the opposite than others. Maybe we should add some consistency, say ordering by id or by name... at second level, so all DBs behave the same.

B) The detailed user list always orders by last access. I'm not going to evaluate if that's ok or no, but for sure it's not obvious and some tip should show that. Alternatively... it should support the same sorting than the brief list...or maybe disappear completely and bring all the functionality to the brief list. --> Will be fixed in MDL-51265 

In any case, those are the details, to be fixed whenever the participants page is evaluated.

For your entire consideration, ciao