Allowing the energy flow INTO the solar panel (photovoltaic), what happens?
There's two things here:


short circuiting the panels to measure current
back-feeding current in the "wrong" direction (such as from a battery)


The first is apparently a normal way of measuring current output for small panels. Provided the meter can take it, it's for a short duration, and the total current isn't expected to be at levels with severe arcing, it's fine. So don't try it on a whole 4kW array.

Note that the total heating is limited by the sun: there's no way for the panel as a whole to get hotter due to electrical self-heating than a black sheet of the same size! Although you may cause localised heating at joints.

The second is bad for panels, as you're reverse-biasing them. Most systems with batteries will contain an ordinary diode to prevent this.

You raised the possibility of heating the panels to self-clean them, which is interesting but I suspect very inefficient.