The mouse position often translates to the wrong chart component.
Which chart component exactly, seems to depend on:
a) the mouse operation in question: hovering, left-clicking, right-clicking,
double-clicking (not sure about dragging)
b) the selection state (i.e. which component was selected),
c) the chart state (i.e. whether it's been "opened" via a double click or not).

This behavior is most confusing, hence the P2 marker.

E.g. any point on a label of the X axis will give me these reactions:
* Hovering will give me a tooltip that says "X axis".
* Right-clicking will pop up a context menu of whatever subcomponent is
currently selected (I'd have expected that it will select the X axis and pop up
its context menu).
* Left-clicking will deselect whatever is selected right now (I'd have expected
it to select the X axis).
* Double-clicking will deselect whatever is selected right now (I'd have
expected it to open up the properties dialog of the X axis).

E.g. when hovering over a point outside any component, I get a tooltip of
"Diagrammfläche" ("diagram area"), and:
* If nothing is selected, left-clicking will select "Diagramm" ("chart", i.e.
the middle area with the axes and the graphics);
* if the middle area is selected, left-clicking will select "Diagrammfläche"
("chart area", i.e. the entire area of the Chart control).

I'm pretty sure that numerous other "strange results" can be produced. The
selection behaviour of Chart is simply a mess, AFAICT.
IMHO, it should go along the following lines:
1) Every point of Chart should be "owned" by a subcomponent.
2) Hovering over a point should display the tooltip that belongs to the owning
subcomponent.
3) Clicking (left, right, or double) should first select that component, then do
the Right Thing for the kind of click (select for left-click, display context
menu for right-click, open (with a subcomponent-specific definition of "open")
for double click).