Even basic stuff like keeping track of when you're actually in front of your computer or idle doesn't work properly in Lync. I'll be typing away for hours and it thinks I'm "Idle: 2 hours" to other people in my contact list.
Then there's the whole, "You can't add this person to your contacts because they have been added to too many other people's contact list" problem. W T F ? How is that even possible in this day and age? Sigh.
Subscriber limits are also a joke. Although I'd be happy to be able to add contacts to my list, or even at times, see the people that are already there. Turning off the integration with Outlook (because it does awful things, like locking your .pst/.ost files so you can't open Outlook and Lync at the same time...) seems to screw up all the contact list related stuff.
This was on Windows 7.
The problem seems to have been solved when we upgraded to Skype for Business a few months ago. There were a lot of other weird nonsensical bugs like this too, but that one was the one that caused me the most grief. Lync was been by far the worst piece of chat software I've ever used.