When I offer a draw in online, I usually say something in the char box too, in case they miss the offer.
I can't be sure, but I'm almost certain that this works, since I started doing this many more accept dead drawn positions.
Now, Is it bad form to offer a draw, and point out the drawing line to your opponent?
When you continue to play after a draw offer from your opponent this IS declining the draw offer.
Normally, I'd agree with you. But in the case of turn based games here, several people in this thread have stated that the draw offers sometimes aren't obvious enough. Coding something into the site to make them stand out more, like a message that asks "By making a move, you are decling your opponent's draw offer. Are you sure you wish to do this? (Yes/No)" when you move would seem to be reasonable to correct this issue.
--Fromper