Join-lines: Vim vs Emacs
Vim has a very simple system to join two lines. All you have to do is press the J (uppercase) key inside the line above.
In Emacs, instead, you must use the C-^ binding in the lower line.
But the Emacs solution may seem a bit more laborious if you use a keyboard with US International Dead Keys layout in MS Windows or GNU/Linux.
However, with a few small adjustments, it can become super-efficient.