When I use the append tool, it's usually part of my ETL process. In that process I have a layer joined with a table that I am appending to another layer. Because of that join, my source layer field names are qualified and look like this - sde.DBO.Ownershiptable.NAME and my target layer field is just NAME. The field mapping component of the append tool doesn't auto match the fields because of the join. I would love it if the append tool looked at just the actual field name instead of the fully qualified field name when auto-matching field names. This could be added to the Environments tab of the tool.