That reddit post is outdated now- it was working off the assumption that it couldn’t have been Malchor, but ANet has specifically opened that possibility up again. Similarly, the “where his father had fallen” thing could easily refer to Malchor, since Dhuum was defeated in the area known as Malchor’s Leap; alternatively, taking into context the full quote- “Standing before his immortal mother, Grenth claimed his place among the gods. Where his father had fallen, Grenth would rise.”- it could have referring to his father being mortal and so dying, while Grenth became an immortal god.
R.I.P., Old Man of Auld Red Wharf. Gone but never forgotten.