I am guessing your developer UGHHHH
Perhaps the above sentence is a bit to esoteric leading to the ambiguity you have experienced. We'll look into rewording it.
The sentence is making two separate statements, the first part is a direct response to the transaction malleability issue which had affected MtGox. The second part is referring to an issue which befell poloniex, their withdrawal system did not check for negative balances and thus a user could become 'overdrawn' due to other issues in the way their withdrawal code was written.
https://bitcointalk.org/index.php?topic=499580When we were developing our service we trawled through many exchange theft threads with the purpose of securing ourselves as well as we can.
Transaction malleability is a keyword buzz for bitcoin. All real bitcoiners know Transaction malleability is a non-issue. So gratz on solving a non-issue!
Also look (0=>balance then !withdraw) I solved non-negative values being able to withdraw. I am so l33t. Again another non-issue but since you want to look like your cool, you threw it in there.
This sentence builds on the 'polling databases for negative balances' statement. We check the arithmetic of all actions the user has made since their balance was last 0. This includes cross referencing new deposits on our db with the blockchain just in case there was a large fork and our main daemon was on the wrong side past the deposit confirmation threshold.
Again keyword buzz for bitcoin, we protect against forks of the blockchain. Honestly as someone that has lived thru a few forks this is again a non-issue, but thank you for solving it. Daemons are quite robust for this situation. SO YEAH.. tell me again how you amazing your backend wallet is I can't wait to hear more.