One example is the "so you also" of Luke 21.29-31. Bernard and I debated that one for a while, but I am still quite convinced that it trends in the direction Marcion -> Luke.
May I ask you: Who do you think the "you" in "so you also" stands for in gLuke, and the corresponding passages in gMark, gMatthew & gMarcion?
Another example is the spot where the gospel begins. It seems likely that some version of Luke actually began at 3.1, since the birth narratives are of a different character than the rest of the book and 3.1 makes a fine beginning for a gospel. Well, that is where Marcion begins. (It is also, by the way, where the Ebionite gospel apparently began.)
I thought I covered that with my third argument (from http://historical-jesus.info/53.html
>> 4) Lk 5:33 "And they said unto him, Why do the disciples of John fast often, and make prayers, and likewise the disciples of the Pharisees; but thine eat and drink?"
Tertullian's 'Against Marcion', IV, 11: "Whence, too, does John come upon the scene? Christ, suddenly; and just as suddenly, John! After this fashion occur all things in Marcion's system."
"Luke" thoroughly introduced John, son of Zechariah, in chapter 1, and in chapter 3, described him as a very popular baptizer & preacher (therefore with his own disciples). So the mention of disciples of John in 5:33 is of no surprise.
However, as noticed by Tertullian, the sudden appearance of disciples of a "John" in gMarcion 5:33, with no further identification, is a sure clue Marcion was working from a gospel (gLuke) and truncated it (eliminating all occurrences of John the Baptist before Lk 5:33). And all other canonical gospels described John at their beginning, well before Jesus starts his public life. <<
Actually, on this thread viewtopic.php?f=3&t=1765#p39307
, I wonder why everything before Lk 4:41, except for 3:1a and maybe 4:14-15 is not in red, according to Tertullian's aforementioned remark, and also that one "In the fifteenth year of the reign of Tiberius (for such is Marcion's proposition) he "came down to the Galilean city of Capernaum,""
Finally, Luke 4.23 famously has Jesus say, "No doubt you will quote this proverb to Me, 'Physician, heal yourself! Whatever we heard was done at Capernaum, do here in your hometown as well'" (NASB). Yet at this point in Luke nothing of Jesus having previously been to Capernaum, let alone having done anything noteworthy there, has been narrated. Luke has both added this line (neither Matthew nor Mark have it) to the Nazareth pericope and moved it so far forward in his gospel that the line he added no longer makes much sense. This suggests a two-stage process: (1) this line was added when the pericope originally stood at a different point in the narrative, parallel perhaps to the Marcan or Matthean position; and (2) later the pericope was moved forward to where the added line no longer works. But the Marcionite gospel has Capernaum before Nazareth, the more primitive order, as it were.
Primitive? Why not corrected by Marcion?
Then of course, for the priority of gLuke, we have the testimonies of Irenaeus, Tertullian & Epiphanius. That must count for something.
And they are signs, through internal & external evidence, that gLuke was written in the 1st century: