In the new composer, type something and press return.
Actual: The new composer inserts a double-line paragraph break.
Expected: When I press return once, it should insert a single-line break, converting it to a paragraph break when I use two lines.
I sense that maybe the Discourse developers actually like it this way, but it’s really bad. No rich-text editor I’ve ever used does it Discourse’s way.
At a minimum, there should be a way to turn this paragraph behavior off.
I would have to agree with this, the behaviour of the new composer is strange and unintuitive when it comes to a simple thing like pressing return. Between this and a bunch of other immediate bugs that I’m trying to reproduce, I would have to say that this is a feature which doesn’t quite feel ready for prime-time yet. 
If the new composer were the default at the moment for example, posting on my site would be completely broken, as many times I’ll post images that I have hosted at Flickr.
이 문제는 의도된 동작이므로 Contribute > Feature 채널로 옮깁니다. 다만, 이 설계 선택이 마음에 들지 않는다는 점은 충분히 이해합니다. 내부적으로 논의 중이며, 곧 더 많은 정보를 공유하겠습니다.
버그를 재현할 수 있게 되면 새로운 주제를 개설해 주십시오 (Flickr 링크가 어떻게 깨져 있는지, 즉 어떤 문제가 발생하는지에 대한 추가 정보를 제공해 주시면 감사하겠습니다). 이 주제는 원 게시자의 코멘트에 집중하도록 합시다.
Very sorry, I will keep the discussion on-topic in the future!
I did post a bug regarding the issue with inline image links in the appropriate forum, hopefully that was the right place for it!
Sorry, in my last post I forgot to actually link to the bug that I had posted:
Keep in mind
SHIFT ENTER
will work
I am not 100% convinced we should change our default, but agree there is a bit of lack of parity with the raw composer.
Do “normal people” know about that chord?
Even if you know, it will still be difficult on touch devices without an external keyboard.
Understood.
But
should we encourage people to
type like this
Or
is it an outlier way of typing content, and generally we want to encourage tidy paragraphs?
Markdown original spec is so adamant this is a bad pattern it makes you insert a \ at the end of the line or double space to line break.
It’s less common but we’re not completely alone in this, notion.so and medium.com work this way as well — generally the idea is to encourage more structure.
I’m also finding it very difficult to switch from previously pressing enter twice to do a new paragraph to now having to only press it once.
There doesn’t seem to be a way to do a single line break on mobile.
FWIW, Shift+Enter using an actual keyboard also doesn’t work with mobile 
I guess we could add an “insert line break” item on mobile behind the plus, it would provide an affordance
FWIW, while it doesn’t bother me personally, this behaviour has also caused confusion among quite a lot of people in my community who were not familiar with the Shift + Enter shortcut (or didn’t expect to be able to use it).
For anyone, like me, who landed here trying to understand how to do the Shift + Enter equivalent on touch screens, there’s a trick here: