SQL Server FTS get tokens from string
You can use DMV sys.dm_fts_index_keywords_by_document to list the words for a given document, eg something like this:

SELECT DISTINCT display_term
FROM sys.dm_fts_index_keywords_by_document( DB_ID(), OBJECT_ID('dbo.Users') ) X


I had a play with this product a few years ago that does hit-highlighting, it was quite nice but I didn't go past the 30-day trial.