См. BOL:

Planning for Merge Replication

text and image Data Types in Merge Replication

Merge replication supports the replication of text, ntext, and image columns only if they have been updated explicitly by an UPDATE statement because it causes a trigger to fire that updates meta data ensuring that the transaction gets propagated to other Subscribers.

Using only the WRITETEXT and UPDATETEXT operations will not propagate the change to other sites. If your application uses WRITETEXT and UPDATETEXT to update the text or ntext columns, explicitly add a dummy UPDATE statement after the WRITETEXT or UPDATETEXT operations, within the same transaction, to fire the trigger and thereby guarantee that the change will be propagated to other sites.