If it was set-up incorrectly then I cannot deny it gave me a boost over others at a critical stage and will happily accept any thing that comes my way.
How did it give you a boost over everybody else?
Everybody could do this. The wording made it seem like it was possible to do it with worse terms - anybody could have taken 30 seconds of their time and experimented to see what the bank would allow them to take. There were references to the maximum loan permitted all over the forums...
If the text said "you may only take a loan if the value of your security is equal or greater than the loan", and this was there I would agree with you. It would be clear that it was a bug and that you should not use it, and that it should be reported immediately. It would be unreasonable for anybody else to use it, because it would seem like it would be impossible to do. Therefore, it would be taking advantage over others, because they would not logically do the same behavior.
Compare that to what is the case. The text made it seem vaguely like you could take a bigger loan than the value of the security. A little reading comprehension, and this seems clear. Therefore, it is reasonable for everybody else to also participate in the same behavior, since the text on the screen makes it seem that the loan system should work as it did. Therefore, while you did gain an advantage, I don't think that it was unfair