I have a question about the Lock Strategy found on Sheldon Brown's web page. https://sheldonbrown.com/lock-strategy.html
Does leaning your bike and bike chain against the object you lock your bike to, excessively, lead to grease rubbing off the chain, or some kind of long term problems to the chain; and stain the object you lean it against. Before I always thought of just locking the down tube (and the down tube of the frame, whenever possible), so the chain was never leaning against anything. Also, I think people mount and dismount on the left side to avoid getting stained from the chain and chainring.

OR should this not be something to be concerned about?

If you just lock a little higher up, you should be able to avoid touching the chain, right? Not that you'll cause any problems for your chain, just get your lock greasy.