When I submitted my Sociology M.Phil study proposal, the adviser wrote in the comments section:
Very good in theory, not at all very good in practice.
That sounds odd. What creates dissonance is the juxtaposition of "not at all" and "very good" which are opposite in meaning to each other.
I suppose "not very good", "not so good" or "not at all good" would have been more typical constructions.
Research done: I Googled the exact phrase and found a few examples, usually in reviews. It's definitely not commonly used.
Recent example:
[…] I am not at all very good at this game as many here like to point out […]
Another recent example for "not at all very":
[…] the way they treat their workers is completely unfair and not at all very professional […]
Source: https://www.indeed.com/cmp/Gms-Mine-Repair-&-Maintenance/reviews
Is "not at all very good" correct usage? Also, how should it be logically interpreted on an arbitrary 6-point scale of quality from 'very good' through 'good', 'not very good', 'not at all very good', and 'not good' (I am not sure those 4 points are sequential) to 'not at all good' which basically means 'bad'? Please give your reasons why or why not and try to support them with adequate references to avoid any objection of being "primarily opinion based."
Note: I am not sure I used the appropriate tag. Please advise or edit.
Best Answer
It isn't that it's wrong but that it isn't used literally. It's euphemism by understatement. Or understatement by euphemism.
"Not very good" literally means "of some level of quality that one couldn't call 'very good'", which could include "good", "fairly good", "fair", "mediocre", "bad", "very bad", "abominable", etc. But we understand it to mean "bad" or worse.
It's like saying, "Doreen isn't exactly a brain trust." One wouldn't say that if one considered Doreen to be of reasonable intelligence, or even average intelligence. One would normally say that to imply the more direct "Doreen is really dumb".