Canonical has already frustrated a former top contributor to Compiz that is an ex-Canonical employee and now they are also alienating Martin Gräßlin, the KWin maintainer for KDE.
There was already some flinging between Mark and Martin in Shuttleworth On Mir: "A Fantastic Piece of Engineering". Martin thinks that Mir is useless and not any better than Wayland and he will not accept any distribution-specific patches, should any arise, but Canonical has never contributed to KWin anyways. Shuttleworth meanwhile feels that KDE/KWin will come to Mir since their display server is said to be so great, albeit it's in its very infancy.
Gräßlin has now written Reply to “All the faces of Ubuntu”. Martin calls out Shuttleworth for not using KWin when he says it will work on Mir and is also Qt-based. He then goes on to tell Mark that he doesn't know how to write KWin, there's been no Canonical contributors to KWin, no Canonical employees have contacted the KWin team about Mir integration, other software abilities have Canonical have been called into question, and Canonical never helped KDE get to run on Wayland.
The German KDE developer added, "I have to ask you to keep KWin out of the pro-Mir campaign. I didn’t ask for Mir, I don’t want Mir and reading blog posts like the one which triggered this reply does lower my motivation to ever have anything to do with Mir. Mir is an answer to a question nobody asked. It’s a solution to problem which does not exist."