@sebikeller could I ask you to write a test that covers this change?

@sebikeller - I've just tried adding some integration tests to master that add white spaces to values and notes at beginning and endings of multiple lines and I can't reproduce your problem.
If you could add an integration test that fails without your change we can review this PR better.
Thanks,

I agree, with an integration test, its not possible to reproduce the problem.

But if you open the generated file with excel, you'll see the difference.

branch master

exceljs-master.xlsx

applied pr

exceljs-pr896.xlsx

Recreating the file in excel, following xml can be extracted:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<comments xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
  <authors>...</authors>
  <commentList>
    <comment ref="A1" authorId="0" shapeId="0">
      <text>
        <r>
          <rPr>
            <b/>
          </rPr>
          <t>First Line:</t>
        </r>
        <r>
          <t xml:space="preserve">
</t>
        </r>
        <r>
          <t xml:space="preserve">Second Line
</t>
        </r>
        <r>
          <t xml:space="preserve">Third Line
</t>
        </r>
        <r>
          <t>Last Line</t>
        </r>
      </text>
    </comment>
  </commentList>
</comments>

Since we cant recreate it with an integration test, it actually means, that the exceljs parser has difference with that of excel.
So you might consider adding a trim() to text values unless xml:space="preserve" is set.

@sebikeller - agreed! I'll add a unit test on the strings xforms to keep a check on this...