Aren't a ton of Lemmy users from Reddit? That being said, I've had more positive interactions here than on Reddit, but I haven't been on Lemmy that long.
The subset of users that switched to Lemmy is smart enough to get over the "select an instance"-hurdle and fine with being on a smaller website with less content. This results in a different kind of interaction. Poeple here seem to still remember that there are actually living people behind those usernames. If Lemmy keeps growing there will be more chances to have the proper "go fuck yourself"-kind of interaction we are used to.
Since Lemmy isn't for profit I think that'll delay features that cater to the lowest common denominator, thus extending our current period of quality discussions.
The "hurdle" seemed huge to me until I actually made the switch, because of how people on the web talk about lemmy I had thought it must be super complicated and cumbersome to use with all the different instances. Once you realize that instances are federated and that all you actually have to do is to simply choose one instance and create one account to see all federated instances, the percieved size of the hurdle shrinks significantly. Now I´m so glad I left reddit with all those karma farming circlejerc subs and all the advertisements.
To be honest i think it is just number and bell curve. A smaller user base will have less extreme, and strangely more opinions as no critical mass for a general trend to be form. Just my guess and source is trust me bro.