Well, that's not a functional barline, it's just printed. It's
similar to putting ":|" which prints a repeat sign, but doesn't
cause LilyPond to recognize the previous section as repeated. I
guess NR 1.2.5 could make this clearer.
original paragraph:
This and other special bar lines may be inserted manually at any
point. When they coincide with the end of a measure they replace
the simple bar line which would have been inserted there
automatically. When they do not coincide with the end of a measure
the specified bar line is inserted at that point in the printed
output. Such insertions do not affect the calculation and
placement of subsequent automatic bar lines.
proposed revision:
This and other special bar lines may be inserted manually at any
point. When they coincide with the end of a measure they replace
the simple bar line which would have been inserted there
automatically. When they do not coincide with the end of a measure
the specified bar line is inserted at that point in the printed
output.
Note that manual bar lines are purely visual. They do not affect
any of the properties that a normal bar line would affect, such as
measure numbers, accidentals, line breaks, etc. They do not affect
the calculation and placement of subsequent automatic bar lines.
When a manual bar line is placed where a normal bar line already
exists, the effects of the original bar line are not altered.
If anyone likes this change, feel free to make it;