Because lemmy is much smaller, you tend to rub into the same users more often. So if someone comes off as abrasive, blocking them can have a notable impact on your experience.
Dogpiling is worse, and it can pay to know what instance the community you're posting in is, as the games community on hexbear is going to be different than on world.
It's much more "left" than reddit. Notably, while this instance, lemmy.ml, is the flagship instance run by the lead dev, the "ml" stands for marxist-leninist.