I don't believe I am explaining MWI instead of arguing against it... whatever has this site done to me? Anyway, grossly simplified, you can think of the matter as being conserved because the "total" mass is the sum of masses in all worlds weighted by the probability of each world. So, if you had, say, 1kg of matter before a "50/50 split", you still have 1kg = 0.5*1kg+0.5*1kg after. But, since each of the two of you after the split has no access to the other world, this 50% prior probability is 100% posterior probability.
Also note that there is no universal law of conservation of matter (or even energy) to begin with, not even in a single universe. It's just an approximation given certain assumptions, like time-independence of the laws describing the system of interest.
LOL @ your position. Agree on most.
Disagree on the conservation of energy though. Every interaction conserves energy (unless you know of time-dependent laws?). Though nothing alters it, we only experience worlds with a nontrivial distribution of energies (otherwise nothing would ever happen) (and this is true whether you use MWI or not)
This is a thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. The previous thread is at close to 500 comments.