You should only have one spell of each type written in on the right hand side of the book. If you are able to write in copies of the same spell on the right hand side, then that is a bug. Not a damaging one though, since you can erase them with the new option provided.
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Devoted member of the
Ironworks
Loyal guardian of the
OHF
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Ancients' club
Witness of the
4,000th post by
Cloudposter
Currently engaged in the
Throne of Bhaal expansion set