Thanks, Kathey. I took that as a +1 to the patch, and committed it to trunk with revision 1363662. Marking this issue as resolved.
I'm in favour of making the indentation style consistent, and now is probably as good a time to do it as any. Making merging difficult has been the main reason why we haven't done it before. If svn handles that now, I guess the main argument against it would be that it would be more difficult to check with svn annotate when a code fragment was introduced. But maybe the same flags could be used with svn annotate.
(I'd probably be in favour of making this change even if the problems with merging and annotation weren't solved, though. Backporting may be a little painful in the beginning, but the old branches will become less relevant and backporting to them will happen less frequently as time passes. The sooner we do it, the sooner the pain will go away.