Hi Walter,
This is one of those wierd ones that happen now and then. Nils Lindquist changed his last name when he moved from Hemling, Björna to Flarke, Gideå. His birth name was Nils Olofsson born in Björna, his father was Olof Nilsson b July 15 1796, his mother was Magdalena Pehrsdotter b May ?31? 1808.
You can find the Olof Nilsson family along with Nils and his wife Anna Cajsa (Katrina) Nilsdotter at GID: 2033.23.86200. Check all the dates and you will find that they all match. The answer to why he changed his surname can probably be found in the notation on the righthand page. The notation says that both of them were accused of arson but were aquitted by the court. My guess is he changed his name to start anew, giving them a clean start in their marriage. He used his birth name Nils Olofsson on their marriage record, the marriage record can be found at GID: 2033.8.110700.
Hope this helps you!
Have a nice day!
Don