you are making false advertisements - you do have a house edge and it is 2% for a 50/50 bet.
I bet 1 BTC
You deduct 0.01 BTC.
I win and claim (2 x 0.99 BTC) 1.98 BTC.
your house edge is 2%
Did you see this in the topic?
Example:
If you bet BTC0.1 against a player, and you win, you would be returned BTC0.199, total profit being BTC0.099
The remaining BTC0.001 goes to house.
It's obvious only reductions are done when the bet is finalized and only on the amount you won, not the total amount.
So to make it really clear let's put it in terms of your example.
I bet 1 BTC, someone accepts my bet and loses his 1BTC.
Now of that 1 BTC that he lost 1% is calculated as a rake, which is 0.01 BTC.
Hope that clarifies things.