Oh, so it is. Post #60 was in early 2016, post #61 was recent (mid-2018).
Still, Morlock's participation ended in 2016 and there were several posts afterwards, before the thread went dormant. I wonder if Morlock was satisfied with the extent to which other people contributed to the advancement of his goals... you know, as in the outcome of successful persuasion, or the outcome of successful magical influence. (shrug) I will probably never know.
Anyways, at no point as a 5E DM, have I thought "this could be a better story, if only the PCs could cast the Imperious Curse (a la Harry Potter)".
If that level of control were widely available, then the question of which NPCs could cast it, would become significant; would cities be ruled by those who can cast it, or by someone using magical control over the designated, enthroned rulers? If the PCs start at first level, and approach 9th level, are there NPCs who take active measures to enthrall any arcane casters who hit level 9, to co-opt them *before* they can start assembling their own faction of thralls? Who has "Un-Nerfed Enthrall" in their spellbooks, and how willing is any wizard to let another wizard copy that spell from one book to another?
Would human society become a magocracy, ruled by arcane casters (whether openly or otherwise)? If the setting involves a god or gods, would they be okay with magocracy or would they raise objections? Would paladins have a particular role in society, since at level 6+ they become harder to keep under control?