I long thought that the micro- macro- distinction was a creationist invention to evade the obvious evidence for evolution. (I still think you see it used mainly by creationists and people who argue with creationists and get sucked into using their terms, but I seem to recall there are exceptions out there in the real literature.) Certainly the bar for macro- as determined by creationists is always something that hasn't been seen yet.
Nebby will disagree but I see no reason micro- changes (individual muations) do not accumulate forever to drift populations isolated from each other arbitrarily far apart. No anchoring, limiting mechanism has ever been identified to me.
There is a very large difference indeed between micro-evolution (if it can even be called evolution) and macro-evolution. Genes are very complex. They consist of chains of from a few dozen, to a few thousand amino acids. You can often change one amino acid in a part of the chain for another without destroying the function of the gene. This can occur by random mutation and be the source of small differences between individuals in a species. Now for macro-evolution to occur, you need completely new genes, completely new functions. This would take the construction by random chance of long chains of amino acids in the exact correct order, it would take other parts of the body recognizing, controlling and making use of this new function. This is quite a task for random mutations to accomplish (which by everyone's admission are quite rare in the nature of things in the first place and detrimental to the individual more than 99% of the time). That is why the challenge to evolutionists is to prove macro-evolution and why this challenge has not been taken by any here or indeed anywhere else.