Outline view. Click on one link & several others are selected & the note text is a concatenation of all the notes. Selecting in adjacent note and using the arrow keys selects only the desired note.
I can’t see how to break this behavior.
If, in map view, several notes precisely touch each other, they form a composite. Selecting any part of a composite selects the whole thing. For example, you might have a composite for a lecture that contains separate notes for the speaker, the title, the topics discussed, and issues that arose in subsequent Q&A.
If you want to remove a note from a composite, just option-drag it away.
Ad you say you are in Outline view you can either switch to map view and option-drag as above. Or with the composite selected in Outline view use Edit → Break Composite.
More on composites.