Apple - Tabs to spaces in BBEdit

The Auto-expand tabs preference must also be set for the Language mapping setting. Also, the setting won't be applied until you create or open a new document.

See Languages in BBEdit.

This has stymied me for quite some time, and today I found the way to enable this for open documents. At the very top of the Document in BBEdit in the left hand corner, you will find the path of the file you are currently editing immediately preceded by a small gear icon. Click the gear icon and place a check in the box next to "Auto-expand Tabs".