[Rebuild] About keeping and removing tags

[errt at gmx.de]

We should certainly do that, there's lots of valuable information that 
can and therefore should be kept. The interesting point is: What 
algorithm do we use to decide on what is a clean override and what is a 
derivation? Something like Levenshtein distance might be worth 
considering. There's also a point in just saying every change can be 
kept, as the changer apperently has some knowledge, otherwise he 
couldn't do the change (ok, that's not true with typo correction, but 
the question is: How many such cases are there?), but we could do that 
just like the current decision on splits and merges: Keep it and if 
anyone complains, remove it. That would most certainly be ok for most 
cases and has the advantage of being really easy.

Dominik