The following bug has been logged on the website:
Bug reference:      13440
Logged by:          Mike Gradek
Email address:      mike(at)busbud(dot)com
PostgreSQL version: 9.3.5
Operating system:   Mac OS X 10.10.3 (14D136)
Description:        
Sorry, I couldn't install the most recent minor release, but I did try this
on several different versions. I used Heroku to try a 9.4.3 build, and got
the same results
select 'ț' as input, unaccent('ț') as observed, 't' as expected;
 input | observed | expected 
-------+----------+----------
 ț     | ț        | t
(1 row)
Let me know how I can help resolve this bug, or if it's expected.
Best regards,
Mike