"you and gbaike are welcome to revive the discussion but MAKE IT BRIEF"

Ok.
From Mercury surface the Sun goes from a diameter of twice the size of the sun as seen from Earth to about 3 times this size. The result of this is it has as low as 5000 watts per sq meter to about 12,000 watts per sq meter.
Mercury's solar constant about 9000 watts per sq meter.
Mercury's orbit is highly Eccentric, it's orbital distance at it's Aphelion is about 51% further from the Sun as compare to it's distance at it's Perihelion.

If Mercury's Orbital Eccentricity wasn't 0.205, and was instead similar to Earth's Orbital Eccentricity of 0.017, then because of it's nearest to the Sun, it probably would have been tidal locked- so that only one side faces the Sun.
In a sense, Mercury is actually tidally locked but only during the time it's at Perihelion- and Mercury or any other planet around any star can not become completely tidally locked IF it has a highly eccentric orbit.

The result of this partial tidal lock, is that the Mercury day and nite are very long- but not forever as it would be if tidally locked with a star.
As illustrated:
Mercury day