Note: Titles are similar but this is a different issue than Square brackets make WordPress ignore newline/paragraph

I'm using the classic editor in the latest version of WordPress. To have the visual editor generate a line break (<br>) instead of a new paragraph (<p>) I use Shift+Enter. The visual editor shows this:

line 1
line 2

If I just use Enter, I get this (indicating a new paragraph tag):

line 1

line 2

The problem occurs when line 1 ends with a square bracket, like so:

line 1 [C]
line 2

it looks okay in the visual editor but the browser renders it as a single line:

line 1 [C] line 2

Looking at the HTML source, the first example inserts a <br /> for the newline while the second example inserts an actual newline \n (which is just generic whitespace in HTML and doesn't start a new line).

Can anyone explain why this is happening and how to fix it?