Isolation level is relevant for a lot of reasons, including Phantom readings.

So far, there's no documentation detailing what Isolation level eZ Publish should require or, at least, advise for MySQL.
Most of eZ Publish users will use the database set for default, what means REPEATABLE-READ.

It would make sense to have documentation on required and advisable Isolation levels for eZ Network, namely on READ-COMMITTED, that works similar to Oracle databases.