The Too Long; Didn't Read Version of Wishful Exegesis, Jephthah's daughter edition

In case you don't have time or interest in reading the more complete response (here), here's a nearly twitter length response to the false claim that Luke quoted verbatim from Judges 11.

1. Luke was Quoting Mary

Luke 1:39 Then said Mary unto the angel, How shall this be, seeing I know not a man?

Mary's phrase, "I know not a man," is a Hebrew idiom that means, "I am a virgin." We don't know what language Mary spoke to Gabriel, but we assume it was more likely to be Hebrew (i.e. Aramaic) than Greek.  Luke translated (we assume) Mary's Hebrew idiom into Greek.  In doing so, Luke used a word-for-word translation method, thereby preserving the Hebrew idiom in Greek words.

2. Mary Using a Hebrew Idiom is Unsurprising

Mary was Jewish.  Her use of a Hebrew idiom does not suggest she was quoting some previous author.  The Hebrew idiom, "not know man" (in various forms) is found in a variety of places.  The Septuagint translates this idiom various ways (see Genesis 19:8, Numbers 31:18, and Numbers 31:35).  Nevertheless, the idiom is not somehow unique to Judges 11.

3. Judges 11 Uses a Different Wording

Judges 11 uses the same idiom but in a different way. In Judges 11 it's a third person singular aorist active indicative, in Luke 1 it's a first person singular present active indicative.  So, once again, not a quotation, even if the root idiom (to not know man) is the same.

4. Similar Idiom Use Abounds

Genesis 19:8 and Judges 21:12 use the same idiom but in the plural, specifically third person plural, aorist active indicative.  

1 Kings 1:4 uses the same (with king rather than man: ὁ βασιλεὺς οὐκ ἔγνω αὐτήν) in a third person singular aorist active indicative, same as Judges 11.

In fact, Matthew 1:4 uses the same as well: καὶ οὐκ ἐγίνωσκεν αὐτὴν, a third person singular, imperfect active indicative.

Indeed, "know not" is just a variation on the Hebrew euphemism "know" to refer to sex, a euphemism that is found multiple times as well (see, for example, Genesis 4:1, 17, and 25; 1 Samuel 1:19).

In short, this is a common idiom, hardly some kind of unique expression found only in Judges 11.

Conclusion

It's not a quotation of Judges 11.  The most one can say is that Mary uses the same Hebrew idiom for virginity, but of course that's not helpful to Roman Catholic (and similar) exegesis.