MySql - selecting into file and re-loading it with special characters
I would suggest remove all those REPLACE(text,',','****') stuff, and use FIELDS ENCLOSED BY...:

SELECT 
  id,
  status_twitter_id,
  twitter_id, 
  creator_twitter_identity_id, 
  text, 
  in_reply_to_status_id, 
  in_reply_to_user_id, 
  urls,
  hashtags,
  created_at, 
  updated_at, 
  sent_at,
  user_mentions
FROM 
  twitter_statuses 
into outfile '/tmp/twitter_statuses.csv'  
FIELDS TERMINATED BY ',' ENCLOSED BY '"'
LINES TERMINATED BY '\n'
;


You then LOAD DATA INFILE like this:

LOAD DATA LOCAL INFILE '/srv/$SPLIT_FOLDER/$f' 
INTO TABLE my_db.twitter_statuses_new 
FIELDS TERMINATED BY ',' ENCLOSED BY '"'
LINES TERMINATED BY '\n'
...


This should do the work.