If you "Check for Duplicate Titles" on Raymond A. Palmer, and use the "Similar Title Mode", the first option it gives you is to merge "Cosmos" with "Cosmos". Attempting to do so results in a Python merge error. The reason for this is that Palmer contributed to this round-table discussion under both his name and that of one of his pseudonyms, "Rae Winters". The result is that the "Parent title" for this title then has Raymond A. Palmer as two of the authors. Consequently, the "duplicate check" is comparing the same title from different viewpoints: One as Palmer and one as "Rae Winters", and hence is suggesting that you merge those two "similar" titles into one. Attempting to merge a title with itself is a bad idea. The Python script should probably give a gentler error message than it does; and the duplicate finder should probably not suggest that particular merge.
Update: It turns out that this was a side effect of Bug 689, "Titles and pubs can have duplicate authors". Now that the other bug has been fixed, the behavior described above should no longer be possible (hopefully.) Closing.
Anonymous
Correction: The bug occurs in both "Similar Title Mode", but also in "Exact Title Mode".
Diff: