Judgement is clearly required here. If too many things seem to be being checked in under this rule, we'll have to set clearer guidelines, but I think that we'll develop a good feel as we go along. I'm not really sure what these would be, but they might include making the compiler easier to configure, improving the packaging, fixing version numbers associated with various things, or what have you. Let's take these case by case. The benefits of every patch should be weighed against the likelihood of breakage.
Small changes are to be preferred to big ones.
Rather than rewriting large chunks of code, we should endeavor to find surgical changes that solve particular problems. In general, the goal is to avoid regressions on the branch.