I know that you could sell the one from the main questline to the orc in the arcaneum, but now there is no option to sell the three i am currently carrying.

I know this is crap, but it looks like a glitch or bug of sorts that doesn't let you remove the scrolls from your inventory. I sold two of them to Dexion but I'm stuck with the last one FFS lol

The scrolls actually weigh nothing even though it has a weight stated. The 3rd you can sell to the orc in the library, but only if you have done skyrim's main quest for that is the same scroll used.

From what I heard the other 2 scrolls can be sold to the Moth Priest.

If you bought the scroll of Urag in the College can you sell it back to him? This is what I did and it didn't work so I'm guessing no.

So is there any additional dialogue if you keep the MQ Elder Scroll anytime during the questline?

Same here, but since it doesn't weigh anything its not so bad.