Does it have any value to keep points in the research area after all the traits have been researched? This could be master writs, mats or something else (from dailies).
Nope, feel free to take them out once you've finished your research, they have no benefit beyond increasing research slots and reducing the time.
I recall reading that once, but I wanted to make sure. I may wait until others are finished though since the cost for that is a bit high, but good to know.
I relocated all the skill points I used in the researches passives to the keen eye after I finished all the trait research.
Master writs or other crafting rewards are not directly dependent of the research passive.
You just really need it to reduce the research times.
"Sweet Mother, sweet Mother, send your child unto me, for the sins of the unworthy must be baptized in blood and fear"
There was a brief mention that the total amount of skill points spent in crafting skill affects the drop rate, but by how much was not said. Experiment, take note what it is with them then how or if it changed for you after removing them.