What it does well
Sees through pretence instantly and commits completely once convinced.
Water · Fixed · ruled by Pluto (traditionally Mars)
☿ Mercury in Scorpio ♏
Mercury governs thinking and speech — how you process and explain. In Scorpio, that function takes on intensity, privacy and refusal to accept surfaces — a Fixed Water expression ruled by Pluto (traditionally Mars).
Where it strains
Tests people rather than asking, and remembers slights for a very long time.
Reading a placement properly
Mercury in Scorpio describes a function in a style. It says nothing yet about where that plays out — for that you need the house, and the house needs a birth time. A placement read without its house is half a sentence.