I have not heard of actual accounts where American soldiers were closing bolts on open chambers during combat. But I did here that it was a feature for Mauser-type actions that a bolt can't be closed on an empty rifle since the follower is designed to come up and get in the way as an indicator it was time to reload. The bolt can be closed with an empty gun, but the follower has to be pushed down.

Then again, I have read (can't recall where) that Civil War soldiers sometimes kept pulling the hammer back and pulling the trigger without loading their muzzleloader. So anything could be possible in the heat of battle, but it is probably difficult to know how big a problem it was.

FWIW, I thought the Harpers Weekly article was a bit "hollywood" and was not written by a military expert.