Python MongoDB Schema feedback

I would dearly love some feedback on the model below. Its a basic commenting structure where Users can comment on a variety of objects in the model. I have denormalised to make querying simpler, but I'm not sure if I've over/under done it. The model tests fine, but it all feels a little clunky. Any feedback would be awesome, thanks.

#####################################################################
# Base ##############################################################
class Base():
    def __init__(self, **kwargs):
        self._ClassName = self.__class__.__name__
        self._Created = datetime.now()
        self.__dict__.update(kwargs)

    def __repr__(self):
        return '<%s>' % self.__class__.__name__

#####################################################################
# Comment ###########################################################
class Comment(Base):
    def __init__(self, username, person, comment, parent, **kwargs):
        self.Username = username
        self.Person = person
        self.Comment = comment
        self.Parent = parent
        self.__dict__.update(kwargs)

    def _save(self):
        #save to Comments
        db.Comments.save(self.__dict__)
        #save to parent collection
        parent_obj = db.dereference(self.Parent)
        query = {'_id':parent_obj['_id']}
        update = {'$addToSet':{'Comments':self.__dict__}}
        db[parent_obj['_Collection']].find_and_modify(query, update, safe=True)
        #save to people collection
        query = {'_id':self.Person.id}
        db.People.find_and_modify(query, update, safe=True)


    def _remove(self):
        #remove from Comments
        query = {'_id':self._id}
        db.Comments.remove(query, safe=True)
        #remove from parent collection
        query = {'Comments._id':self._id}
        update = {'$pull':{'Comments':self.__dict__}}
        db[self.Parent.collection].find_and_modify(query, update, safe=True)
        #remove from people collection
        db.People.find_and_modify(query, update, safe=True)

    def __str__(self):
        return '%s - %s...' % (self.Username, self.Comment[:10])

person = {'Username':'foobarman'}
db.People.save(person, safe=True)

program = {'Title':'the foobar', '_Collection', 'Programs'}
db.Programs.save(program, safe=True)

comment = Comment(
                person['Username'],
                DBRef('People', person['_id']),
                'this is a comment about the foobar program',
                DBRef(program['_Collection'], program['_id']))

comment._save()

# find latest 10 comments
list(db.Comments.find().sort('_Created', -1).limit(10))

# find all comments for username
db.People.find_one({'Username':'foobarman'})['Comments']

# find all comments for program
db.Programs.find({'Title':'the foobar'})['Comments']

# find all comments for program by user
list(db.Comments.find({
                'Parent':DBRef(program['_Collection'], program['_id']),
                'Username':'foobarman'}))