bbPress.org

Thanks for posting back

To remove the indent and the left hand border,
put the following into the custom css tab of the plugin

#bbpress-forums .bbp-forums-list {
  border-left: none;
  padding-left: 0px;
}

If you still want the border, then just

#bbpress-forums .bbp-forums-list {
  padding-left: 0px;
}