I think the larger point is that people, will form a persona on the forum and then craft their conclusions and opinions around that persona. Usually this is done when they strongly associate with one faction.
To take an extreme example from another thread.
Now, there is no way this poster is sincere without ignoring 14 years worth of lore. So either she’s roleplaying as a Draenei Mage, she’s a troll desperate for attention, or she has decided that she is the defender of the Alliance on this forum and she will attack the Horde at every opportunity. Now I don’t think she’s a troll because she’s too consistent for that, which leaves the other two options, both of which are roles she may be playing.
But either way, there is an undercurrent in her posts of not being able to separate her views on this forum from in universe views of her character.
Objectivity in discussing lore is what should be strived for. Obviously not creating a toxic environment is important too, a lesson I can certainly keep in mind, and a lesson that at least one person advocating for it could also remember.
But the issue of roleplaying is one of someone picking a persona, even if that persona is as simple as ‘advocate for my faction’ and then crafting their opinion around that persona. This persons persona is Illidan’s enemy, because she’s roleplaying. But Illidan is not her enemy, because Illidan isn’t real, and neither is her persona.