If I would have a .player dropping smoke in front of me like that I would probably open a ticket against him with the match recording and screenshots.
The game rules forbid to use tactics that prevent a player to play normally and if is true that as long as the player that drops the smoke spots the enemy continue to spot it also the other one sees it but doing so it at least annoying and prevents the player behind the not wanted smoke screen to spot other enemies, as maybe he can have a better spotting range.
To track the enemy or if possible to designate it are much more fair ways and if I am not wrong the damage done to enemies spotted by others is less rewarded then the one to enemies that you see, if so you don't only annoy that person, but you actually "steal" some of his damage as he is less rewarded while you get spotting damage from his shots.
You can "steal kills" as no enemy tank is private propriety of a player, but you can not prevent the player to play, placing your tank in his line of fire, dropping smoke in front of him (if not to defend him), ramming him away from his position to take it yourself and similar crap ways to play.