Will enabling row movements on list-partitioned table cause performance problems(oracle 11g r2)
You should be fine; the rowid would be a show-stopper if you were using it
Temporarily, there would be "holes" in the data files, but Oracle will fill them in without any intervention.  Ensure you have automatic tablespace management enabled.
You can invoke that command but no need to; let Oracle take care of it
The person that stated that probably meant there was a one-time hit, or he didn't know what he was talking about, or using an old version.  You tested; his environment may have had a rat's nest of views.