If you are at the end of an indented line and hit enter (which will cause a newly indented line to be inserted below), and then move away from the line without typing anything, the indentation will remain.
After hitting enter:
If you don't type anything, the indentation will stay there. There is no reason for this.
This is with the "trim_automatic_white_space" pref set to true.
Latest dev build (2220).