Try the following:
- create a new writer document
- enter 3 paragraphs, let's say
ABCDEFG
QWERTZ

- now insert a bookmark arround WERT in paragraph 2
- select from the start of the document to the Z of QWERTZ so you have a
selection surrounding the created bookmark plus the Z which is not part of the
bookmark
- press CTRL+C (or do any other thing you want to copy the selected range :-) )
- click to the end of the document and press CTRL+V (paste)
- now open the navigator (e.g. by pressing F5) and check the bookmarks
- you'll see, there is only bookmark "WERT", but no copy of it

If you select the paragraph-break after Z and try this again you'll see the
bookmark will be copied. If you select QWERTZ only and paste it, the bookmark is
also duplicated.
I found that the bookmarks in the last selected paragraph won't be copied.

The problem is also reproducable to using OOo-API using XTransferable.