Great detective work!
To clarify (i hope) and expand:
CTRL+K or CTRL+SHIFT+K
USUAL BEHAVIORS
(some text has been selected) -- all instances of the selected text are highlighted. the cursor jumps to the *next* or (with SHIFT) *previous* instance of the text, and that text is selected. If there is no next or previous instance, the computer makes a warning sound.
(highlights are ON) -- the cursor moves to the *next* or (with SHIFT) *previous* instance of the highlighted text, and the text is selected. If there is no next or previous instance, the cursor stays where it is, and the computer makes a warning sound.
(anywhere in the code, nothing selected, CTRL+K has never been used to turn on highlights) -- computer makes a warning sound.
(anywhere in the code (except see above), nothing selected, CTRL+K has previously been used) -- the previously highlighted text is highlighted again, the next or (with SHIFT) previous instance is selected.
SPECIAL BEHAVIORS:
(at the very *end* of the code, nothing selected) -- CTRL+K - The highlights are removed, and the computer makes a warning sound.
(at the very *end* of the code, nothing selected) -- CTRL+SHIFT+K - The highlights are applied, and the last instance is selected.
(at the very *beginning* of the code, nothing selected) -- CTRL+SHIFT-K - The highlights are removed, and the computer makes a warning sound.
(at the very *beginning* of the code, nothing selected) -- CTRL+K - The highlights are reapplied, and the first instance is selected.
(after loading another, entirely different model) -- CTRL+K -- the matching text in this model is highlighted, etc. (!)
~~James