I also like you can't imagine any reason for having a Hot thread Icon, cause we have the number of the replies so every one can estimate how hot is a sample thread.

But still it would be much useful if we could have an option indicating that 'You've posted in this thread'.
I can keep track of the threads where I posted the thread myself, but as for the ones I reply to, sometimes I forgot to refer again to give further answers.

Farshid