I'm happy if somebody find error or bad data and fix it. But please, ask first if you do large area bot edits in different countries.
1./ Why you think is_in tag is wrong import? Maybe it contains data which are somehow used. Maybe not in you county, but in other yes.
2./ ele=0 well, maybe most of ele=0 tag are unnecessary, but all? don't know
Graphomania is not OSM problem, people are problem :)
"bad imports" sometimes are not bad, only unfinished