The sidebar says
This community is the place to discuss and ask questions about anime, anime news, and related topics
Emphasis mine. Episode discussions are created here constantly, so what’s the problem with linking a full legal episode of an anime?
The idea that if it was a trailer it would be fine is ridiculous
I’m probably not going to watch anything hosted on YouTube (I blocked it completely a while back), but I don’t think it’s a big deal if someone links the first episode of something that’s legit freely available (i.e. not pirated) as long as they’re not being spammy about it.
Edit: to expand on that, we’re not exactly getting flooded with posts and that kind of restriction from reddit is more because of volume than anything, I think.
I’m not a mod of course, but I think posting full episode links would overshadow the bot discussion posts. We have those for a reason. At least for seasonal stuff.