There's still a minor bug in regards to smoke particles in the client. Devs are aware of it. The source is either hard to trace, or too localized to be solvable at this time. This is my best knowledge on it. The best theory I know of is a problem in local video drivers or hardware, though there may be other causes.
Couple of threads on this in bugs.
viewtopic.php?f=47&t=57517&p=742244&hilit=smoke#p739347 (missing original image posted)
http://www.havenandhearth.com/forum/vie ... 90#p808390 (several examples in this thread)
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