When an QDomDocument is parsed with the 'PreserveSpacingOnlyNodes' option, it gains phantom text nodes that consist of a newline followed by the number of spaces of indentation.

To reproduce this problem, compile and execute attached code.

If you use the 'PreserveSpacingOnlyNodes' option, you will see phantom text nodes in the output (hex encoded to make them more clear) and the all-spaces node is (correctly) preserved. see screenshot.

If you use the 'Default' option, you will not see these phantom text nodes and the all-spaces node is (correctly) filtered out.