Is tianeptine addictive? A recent (2014) study in cell cultures has found that tianeptine is a mu-opioid receptor (MOR) agonist (and [mentioning for completeness] delta opioid receptor agonist as well, albeit weaker). It's been generally proposed that 


  The strong rewarding effect of MOR agonists likely contributes to the reported success of the ‘opioid depression cure’.


So are there reports of tianeptine addiction? Has its addictive potential been studied in more detail?
The internet is flooded with anecdotal reports of 'Tian' relating to the drug's addictive potential after recreational use, for example here, here and here. Often, though, these reports come from people already addicted to other illicit drugs. Notably, tianeptine is used for rehab purposes, just like the partial opioid agonist naloxone. So anecdotal reports can be misleading.

Scientific reports however also indicate the drug's addictive potential. Vadachkoria et al. (2009) report


  Supposedly, Tianeptine, in contrast to other anti-depressants, stimulates release of neurotransmitter dopamine in nucleus Accumbens, that probably determine[s the] addictive potential of this drug.


Addiction can be defined as a syndrome characterized by compulsive substance abuse. In a more verbose definition:


  Addiction is defined as a chronic, relapsing brain disease that is characterized by compulsive drug seeking and use, despite harmful consequences.† It is considered a brain disease because drugs change the brain—they change its structure and how it works. These brain changes can be long-lasting, and can lead to the harmful behaviors seen in people who abuse drugs


It is generally accepted that the antidepressant drugs do not cause addiction. However, tianeptine, among some other antidepressants do have addictive potential (Lapsekili &amp; Yavuz, 2014). 

Reference
-  Lapsekili &amp; Yavuz, J Psychiatry Neurol Sci (2014); 27: 81-4
- Vadachkoria et al., Georgian Med News (2009); 174:92-4