String Pooling for MySQL
Small starting clarification: the article you linked to on InnoDB text/blob storage is a little out of date with MySQL 5.5, and the barracuda row format.  This article is more up to date.

On to your question:

In the schema you have, each row will be less than ~8K, so you can guarantee across both antelope and barracuda row formats that all data will be stored in-line - not requiring external/overflow pages.

If you were to require overflow pages, they are never de-duplicated (which is what I would probably describe your 'pooling' mechanism as).  Even worse than they are never de-duplicated, they are never shared...

If you could have a record too big to fit inline (~8K limit), each text/blob that needs to be moved out will take a minimum of a 16K page to itself.