With the code shown below, I expect to see the following:
(you need to be viewing this in a fixed-width font for it to make
any sense)

Hello World.....................................
   Hello World..................................

but what I actually see is this:

Hello World.....................................
   Hello World...............................

Note that the second line's leader doesn't get to the right margin;
it looks as if the start-indent that I have applied to the second line
is affecting its right margin too.

Here is the code:

<?xml version="1.0" encoding="UTF-8"?>
<fo:root xmlns:fo="http://www.w3.org/1999/XSL/Format">
  <fo:layout-master-set>
    <fo:simple-page-master margin-right="25mm" margin-left="25mm"
                           margin-bottom="20mm" margin-top="15mm"
                           page-height="297mm" page-width="210mm"
                           master-name="a4">
      <fo:region-before extent="10mm"/>
      <fo:region-after extent="10mm"/>
      <fo:region-body margin-bottom="15mm" margin-top="15mm"/>
    </fo:simple-page-master>
  </fo:layout-master-set>
  <fo:page-sequence master-name="a4">
    <fo:flow flow-name="xsl-region-body">

      <fo:block>
        Hello World
        <fo:leader leader-pattern="dots"/>
      </fo:block>

      <fo:block start-indent="2em">
        Hello World
        <fo:leader leader-pattern="dots"/>
      </fo:block>

    </fo:flow>
  </fo:page-sequence>
</fo:root>