ahh this is so interesting!! i've thought about this so much!!!

i think a true s2-s3 helia would basically have a silent attitude of "i fucking told you so" But he would try to help riven understand musa's point of view. honestly, i think helia would ultimately respect musa's decision and might try to tell riven to back off for a while instead of continuing to push them back together. it's not that he doesn't support them or that he doesn't understand riven, but his mini rant in s3 was literally "if you don't respect her, you don't deserve her and she will break up with you" so i can see him being a Little more on "her" side. i think helia would understand that riven pushing musa too early would just make her feel worse since the break up was specifically about her needing peace and time away from him.

musa acknowledges that they have a tendency to bring out the worst in each other, and while i can't say for certain that helia Also knows this, he likely would understand it after the break up at least. so i can also see him trying to get riven to really slow down and stop reacting prematurely so much. a Lot of the muri drama is one of them reacting with the first negative emotion that pops up instead of taking the time to get more information or at least calm down a little. so i think helia, especially with his experience in things like meditation and poetry, would try to get riven to slow down, assess his emotions, and react in a way that doesn't make either one of them defensive.

helia does like gift giving so it's not like. Completely Out Of Character that he might at some point suggest giving musa something to show his affection, but helia does 100% understand that muri's issues wouldn't be solved with some chocolate hearts. he may not understand every single tiny complexity of their relationship, but he does know that riven has a tendency to react first, think later and that he has trouble showing affection in a way musa understands.