Sure, you can't get it perfectly, but you can certainly get a hell of a lot closer than not actually trying! :p (Not a personal "you" 
)
If the jumbo cookies overflow the client, I'm not sure I would classify that as "not perfectly." Weird, unexpected things are bound to happen if you try to store the thread history into cookies, and not just to the titan forums. Cookies are meant to store simple state data. They are not meant to store databases. The last time I did serious programming involving web cookies the practical limit on them was about 1k of data. Not that that was the absolute browser limit, but that trying to handle significantly more data than that would start to cause strange problems with different symptoms on different browsers due to different browsers enforcing different cookie limits in different ways. Some would have a cookie limit. Some would have a cookie domain limit for all cookies in a domain. Some would enforce both overlapping. Some would officially support a certain limit, but start to malfunction below the limit unpredictably. And that is totally separate from browsers that clear or suppress tracking cookies.
If Titan somehow wanted to have a special flag for a very few threads where they wanted the count to be accurate, setting that flag in the browser cookie would work. But in the general case, I think it would go wonky fast. And not just in terms of broken counters, but in terms of odd browser behavior. You don't want to be the cause of that.
