It isn't a crime to bump your thread as far you do it right just as thd26bct has pointed out. Also the motives behind them bumping their thread shouldn't be your consider, focus on the reason why you joined the forum and let others focus on theirs. Even though threads are been bump basically just for merits it isn't a crime as at the end of the day the thread gets more visibility which means more users read them and if it's worth some merit it gets it too. Irrespective of how contributive (quality) a thread is, it still need visibility for it to be rewarded.