There are two issues you need to look at

ISSUE #1 : Characters Vs Bytes

Since UTF-8 uses 3 bytes per characters, you may not have allocated enough for character fields.

ISSUE #2 : InnoDB Row Length

By default, an index key for a single-column index can be up to 767 bytes. The same length limit applies to any index key prefix. See Section 13.1.13, “CREATE INDEX Syntax”. For example, you might hit this limit with a column prefix index of more than 255 characters on a TEXT or VARCHAR column, assuming a UTF-8 character set and the maximum of 3 bytes for each character. When the innodb_large_prefix configuration option is enabled, this length limit is raised to 3072 bytes, for InnoDB tables that use the DYNAMIC and COMPRESSED row formats.

When you attempt to specify an index prefix length longer than allowed, the length is silently reduced to the maximum length. This configuration option changes the error handling for some combinations of row format and prefix length longer than the maximum allowed. See innodb_large_prefix for details.

The InnoDB internal maximum key length is 3500 bytes, but MySQL itself restricts this to 3072 bytes. This limit applies to the length of the combined index key in a multi-column index.

The maximum row length, except for variable-length columns (VARBINARY, VARCHAR, BLOB and TEXT), is slightly less than half of a database page. That is, the maximum row length is about 8000 bytes. LONGBLOB and LONGTEXT columns must be less than 4GB, and the total row length, including BLOB and TEXT columns, must be less than 4GB.

If a row is less than half a page long, all of it is stored locally within the page. If it exceeds half a page, variable-length columns are chosen for external off-page storage until the row fits within half a page, as described in Section 14.3.12.2, “File Space Management”.

Although InnoDB supports row sizes larger than 65,535 bytes internally, MySQL itself imposes a row-size limit of 65,535 for the combined size of all columns:

mysql> CREATE TABLE t (a VARCHAR(8000), b VARCHAR(10000), -> c VARCHAR(10000), d VARCHAR(10000), e VARCHAR(10000), -> f VARCHAR(10000), g VARCHAR(10000)) ENGINE=InnoDB; ERROR 1118 (42000): Row size too large. The maximum row size for the used table type, not counting BLOBs, is 65535. You have to change some columns to TEXT or BLOBs See Section E.10.4, “Table Column-Count and Row-Size Limits”.

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.