No friendly-fire, but you can block your ally's shots. I don't play splatlings but in Salmon Run and it's ever changing weapon rotation I had to get familiar with the weapons, and I got so many teammates already going in front of me while I'm trying to mow down the salmonid waves with my assigned splatling, kind of a pain in the ass, but I guess my teammates got another kind of pain in the ass after doing so ?
Not very nsfw at all, but still, I'll post this on my nsfw account on Twitter so I'm showing it to you guys first.