I don't have enough technical knowledge to give you an answer, but here is what MTR is:
http://en.wikipedia.org/wiki/MTR_%28software%29
RCK will probably be able to tell you more.
I only have experience from reading what server admins said but having some loss does not mean an issue per se because some routers are configured to ignore some requests (always or at a certain interval).
The interesting thing for admins is when there is a huge variation from one router to another (especially when it belongs to to the same provider).