"Which is more correct? This or that?"
There's even "most correct" as in "it is most correct to choose..."
This is due to the simple fact that in many non-trivial fields, correctness is not absolute and thus multiple correct choices or outcomes are valid. Local preferences might recognize this, but prefer one over the other. In noun usage, this is a carryover from verb usage
"My shoes were mostly corrected by the cobbler." is perfectly fine, so users of English also find that "The fit of my shoes is mostly correct." is also perfectly valid usage.
More examples:
Which partial phrase emphasizes, and persuades better a point better (as a matter of rhetoric)?
"It is most correct to take this option."
"It is a preference to take this option."
Of course the former is stronger than the latter.
"correct" clearly grades.
If you're specifically talking about my use of "more correct", let me try another example of why I think "more correct" is useful nonsense. I'm Canadian. Therefore, I use spellings like "colour" and "honour".
However, if I'm writing something primarily targeted to Americans, I switch to honor and color. It isn't that colour becomes incorrect when I write for an American audience. To me, color is always wrong. But, if I want to influence an American audience, color will be the correct spelling they're looking for.
When I'm obsessing over edits, especially when underlying rules are unclear (or non-existent), shades of correctness are the best metric I can find. Do you have another?
You might instead write "closer to correct", but, how clunky.
Meanwhile, you can assign a mathematical measure of partial correctness for, say, sets of statements, simply as the fraction of correct statements over the total. In linguistics, you can assign measures to both acceptibility and correctness simultaneously by taking the fraction of people who "accept" a construct as "correct".
I'm not even sure how many levels of meta I'm at, so I'm done.
Correct \Cor*rect"\ (k[^o]r*r[e^]kt"), a.
[L. correctus, p. p. of corrigere to make straight,
to correct; cor- + regere to lead straight: cf. F.
correct. See {Regular}, {Right}, and cf. {Escort}.]
Set right, or made straight; hence, conformable to
truth, rectitude, or propriety, or to a just standard;
not faulty or imperfect; free from error; as, correct
behavior; correct views.
[1913 Webster]
Always use the most correct editions.
--Felton.
If you are building truth tables, then something is either correct or it isn't. But that's certainly not the case when using words to communicate ideas between humans.
After all, haven't each of us taken a multiple choice test with instructions to choose the most correct answer?
It's no different than choosing the most appropriate programming language for a given project; plenty will work, but ultimately one is the most logical given who will be writing it, reading it, using it, maintaining it, deploying it, etc.
Whether "less [count-noun]" is acceptable depends on granularity: "less than two adverbs" is acceptable whenever it feels alright to you to just abstract adverbs into a pure number. "less than two corrections" is not acceptable to most people because corrections don't lend themselves to being abstracted into a number.
Languages are not random. It's just that prescriptivist get hung up on random subsets of language and pretend they've seen all of it.