Nobody else was given the title "Full of Grace" or "highly favored"
The great Baptist Greek scholar A.T. Robertson exhibits a Protestant perspective, but is objective and fair-minded, in commenting on this verse as follows:
"Highly favoured" (kecharitomene). Perfect passive participle of charitoo and means endowed with grace (charis), enriched with grace as in Ephesians. 1:6, . . . The Vulgate gratiae plena "is right, if it means 'full of grace which thou hast received'; wrong, if it means 'full of grace which thou hast to bestow'" (Plummer).
(Robertson, II, 13)
Kecharitomene has to do with God’s grace, as it is derived from the Greek root, charis (literally, "grace"). Thus, in the KJV, charis is translated "grace" 129 out of the 150 times that it appears. Greek scholar Marvin Vincent noted that even Wycliffe and Tyndale (no enthusiastic supporters of the Catholic Church) both rendered kecharitomene in Luke 1:28 as "full of grace" and that the literal meaning was "endued with grace" (Vincent, I, 259).
Likewise, well-known Protestant linguist W.E. Vine, defines it as "to endue with Divine favour or grace" (Vine, II, 171). All these men (except Wycliffe, who probably would have been, had he lived in the 16th century or after it) are Protestants, and so cannot be accused of Catholic translation bias. Even a severe critic of Catholicism like James White can’t avoid the fact that kecharitomene (however translated) cannot be divorced from the notion of grace, and stated that the term referred to "divine favor, that is, God’s grace" (White, 201).
Of course, Catholics agree that Mary has received grace. This is assumed in the doctrine of the Immaculate Conception: it was a grace from God which could not possibly have had anything to do with Mary's personal merit, since it was granted by God at the moment of her conception, to preserve her from original sin (as appropriate for the one who would bear God Incarnate in her very body).
The Catholic argument hinges upon the meaning of kecharitomene. For Mary this signifies astate granted to her, in which she enjoys an extraordinary fullness of grace. Charis often refers to a power or ability which God grants in order to overcome sin (and this is how we interpret Luke 1:28). This sense is a biblical one, as Greek scholar Gerhard Kittel points out:
Grace is the basis of justification and is also manifested in it ([Rom.] 5:20-21). Hence grace is in some sense a state (5:2), although one is always called into it (Gal. 1:6), and it is always a gift on which one has no claim. Grace is sufficient (1 Cor. 1:29) . . . The work of grace in overcoming sin displays its power (Rom. 5:20-21) . . .
(Kittel, 1304-1305)
Protestant linguist W.E. Vine concurs that charis can mean "a state of grace, e.g., Rom. 5:2; 1 Pet. 5:12; 2 Pet. 3:18" (Vine, II, 170). One can construct a strong biblical argument from analogy, for Mary's sinlessness. For St. Paul, grace (charis) is the antithesis and "conqueror" of sin (emphases added in the following verses):
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