what does evaluation of left shoulder including bright shows
accentuation of the left trabecular markings of the left proximal
humeral diaphysis mean

For what it is worth - my wife is a radiologist and this is what she
said it means.  "Including bright"  means he looked at the xray with
the normal viewer and in front of an extra strong light. Trabecular
markings relate to the honeycomb like structure of the bone - these
were accentuated or more visible than normal.  The "proximal humeral
disphysis" means the top of the upper arm bone at the junction where
the bone transitions from the ball part of the bone to the straight
part of bone.  My wife said this condition is non-specific, that is,
it really doesn't tell you much (maybe kind of like this answer)