How do I replace a newline in Atom?

Looks like Atom matches newlines as \r\n but behaves inconsistently when replacing just the \n with nothing.

So newlines seem to match \s+ and \r\n, and only “half” of the line-ending matches \n.

• If you replace \n with a string, nothing happens to the line-ending, but the string is appended to the next line
• If you replace \r with a string, nothing happens at all, but the cursor advances.