I’ll add a little from myself. In the short time I’ve been on HeroesWorld, I’ve come to the conclusion that reaching a compromise between the versions is unlikely ever to happen, because if there are those who will under no circumstances play SoD, there will also be another person who will not play HotA.
Why does this happen? Simply because these are different versions of the same game, and it doesn’t matter why people prefer one version or another — it’s each player’s individual choice. Even if a new version appears (a fusion of SoD and HotA, some sort of SoHA), some players will still stay only with SoD or only with HotA. So there’s no need to invent anything. Organizers should always set one version as the default (base) when organizing tournaments, and use the second version by mutual agreement if those who prefer the other version are playing among themselves.

Let me speculate a little. I don’t know exactly when soccer was invented, but for example, the English invented soccer and played it. Then came people who liked indoor soccer on small fields more, so they invented futsal, and a new game emerged. Then people went further, and a third group invented beach soccer, forming a third coalition of people who prefer that third game. It’s all soccer, and players intersect with each other in some ways, but they stay and play what feels closer to them, the soccer they chose. It’s still soccer and has a lot in common, but you also can’t really compare them, because they’re different versions.

Wimbledon and Roland Garros were mentioned — Grand Slam tournaments, one game and everything is the same, but the only difference is the surface they play on (grass and clay). Yet that difference is so great that many Tour players never play on one surface or the other in their entire lives. For example, there are players who prefer clay surfaces (Volandri, Verdasco... actually many Spanish players), and throughout the year they only play tournaments ON clay surfaces — you can’t drag them to grass tournaments. They play on grass only to remain in the Association of Tennis Professionals (and because the prize money and ranking points are the highest), but according to Tour regulations, there are mandatory tournaments they have to participate in. From those that players choose according to their preference, they pick clay and that’s it. Likewise, there are grass-court players who try to avoid clay. The same goes for our SoD and HotA.

The only way out, if the goal is to unite SoD and HotA, to merge the HoMM community, is to impose obligations on every player to play both SoD and HotA, just like different surfaces in tennis. Only a MOTIVATOR can force a player to take on these obligations (to play an unloved version) — an organization that can pay MONEY for playing in tournaments.