Gamerescape E3 Interview

[Iscah]

I was originally of the mind it was the same merchant from 2.0's opening and 2.55's ending, and that he was more important than initially assumed

I thought you got rescued in 2.55 by whichever merchant you met at the beginning of the game, though the script on Garland Tools only has dialogue for Bremondt (the Gridsnian merchant). Maybe it works differently within the game, but I can't check now.

Maybe Urianger is calling Y'shtola "Master Matoya" by that name in the OP because it's not actually her, but her double...

Possible, though I saw some character profile slides the other day (from the live letter?) and it does seem to be "our" Y'shtola in the black outfit.

I certainly hope there's a more interesting explanation for it that "just an alias that we deliberately showed to confuse you all when it's barely even a plot point".