I recommend adhering to the LNT guidelines "If more substantial firewood is needed, it should be limited to dead-fallen trees located far beyond the sight of the campsite, privy or shoreline. Ragged, saw-amputated dead trees are definitely not part of the natural landscape!"
When it comes to drift-wood along the shores, I believe it's preferable to remove whole smaller pieces rather than amputating sections and leaving raw saw cuts visible from the water.