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.
I’m moving this to Feature since this is working as designed, though I understand this is not a design choice that you find desirable. We’re talking about this internally and will share more soon.
Please open new topics as you are able to reproduce bugs (and I would appreciate more information about what’s broken with the Flickr links); let’s keep this topic focused on the original poster’s comments.
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.