It really is a frustration for some of my users. Some are poets and struggle to get the format right.

I do not know whether it originates from the Quill plugin or UNA development, but it is these little things that cause some users to leave.

At this stage, selecting all the text and changing the format to "Heading 5",

kinda normalize the layout. (Like here).

So, "Normal" is actually paragraph format, inserting the extra line.