I'm not sure what the problems would be, concretely, but we can always
solve the problem by making the behavior optional.
I think the reason why it was on M-, before was because repeated
M-. couldn't tell whether you wanted the next, or to start a new search
for whatever point is on now.
That's also my understanding, and I'm suggesting that it distinguishes
the two by checking if `M-.` is used consecutively or not (just like
`C-/` can't easily tell whether you want to keep undoing or you want to redo
the thing you just undid, so it checks whether these `C-/` are
consecutive or not).