Problem with delimitMate, gui and combining characters

I'm having this issue with delimitMate, but it doesn't happen with vim or gvim on linux, and it doesn't happen with MacVim on the command line, I can only reproduce it on the MacVim gui, so I'm starting to think the problem isn't the plugin.

Here are the exact steps to reproduce:

1. mvim -u NONE -U NONE -N

2. :so ~/.vim/bundle/delimitMate/autoload/delimitMate.vim<cr>

3. :so ~/.vim/bundle/delimitMate/plugin/delimitMate.vim<cr>

   (the files have to be there, obviously)

4. :DelimitMateOn<cr>

5. i<m-`>a (that's option + `, without macmeta)

   This should type à, but instead it types `à``. It only happens in the MacVim gui, at the command line it works as it should.

6. ```

   This should result in | (| is the cursor), but instead it does just ```. Again, it only happens in the gui.

The steps above use the regular US keyboard profile. I'm actually using the US International keyboard profile, which has many more combining characters, and this happens with others too (so this problem has nothing to do with the meta key, which isn't used with the other profile).

Reproduce the behavior in the MacVim GUI with mvim -u NONE -U NONE -N, sourcing autoload/delimitMate.vim and plugin/delimitMate.vim before enabling delimitMate. Compare GUI input with command-line MacVim for the listed combining-character and space cases; done when both produce the expected character and cursor behavior.