A pretty simple question, what makes jazz lines sound jazzy as apose to some other style of line?
A hard to answer question ... The easy answer is "swing" but not only is that very vague (a good player can convey a strong swing feel using quarter notes) but also doesn't apply to a lot of jazz.

And really, jazz is a stupid vague term: I agree with Metheny, that it's really a verb.

If you want to know what you can do to make your lines sound jazzy, well, that's way easier. Listen, transcribe, play. Three easy steps. Takes a lifetime.
listening to yourself

seriously, the best piece of advice i've ever gotten about playing guitar was from my classical teachers who told me to listen to what I play, not just play it
Quote by beadhangingOne
There is no music but metal and muhammad is its prophet.
i used think chromatics and adherence to elements of chords that other genres dont touch upon, but its actually so much more than that
i dont play alot of jazz but i do know the swing tempo/phrasing idk listen to Planet Caravan amazing jazz lines
^The bebop sound (which, to me, represents the "jazz sound" in the most straightforward way) doesn't focus on scales. At all.

Chromatic approach tones on unstressed beats - essential. But always remember: approach. The lines have to move forward, toward resolution. This is the single most important problem with the scalar approach to improvisation, is that the players miss the essential movement they have to give their lines.
I think harmony ans syncopation are the most important things, not approach to melody.