revs transplanted across branches show files as deleted?

I'm not sure if this is a bug or just some misunderstanding on my part of hg magic with named branches and transplant, but take a look:

https://bitbucket.org/bbangert/pylons/

The project has three branches, and it's common to transplant a change from trunk to the others. Most of the time, when you see these series of three commits, the first one shows that files are modified, and the subsequent ones show that they're deleted! Even the diff and raw changeset views indicate such. {{

}} certainly doesn't look this way – it shows the same patch on each different branch as you'd expect.

Oddly, one recent set of these (pjenvey's commit 'Jython includes an mtime...' does not exhibit this behavior and works as expected.