ACBL states that “The objective of the Alert system is for both pairs at the table to have equal access to all information contained in any auction. In order to meet this goal, it is necessary that all players understand and practice the principles of Full Disclosure and Active Ethics. Ethical bridge players will recognize the obligation to give complete explanations. They will accept the fact that any such information is entirely for the benefit of the opponents, and may not be used to assist their own partnership.” (from ACBL Alert Procedures)
Self-alerting of bids is one of the unexpected benefits of playing on BBO. Only opponents get to see your self-alert. Your partner is unaware that you even alerted, thus minimizing unauthorized information. Of course you have to do it the right way, which means NOT using the chat box. Click here if you’re unsure of how to do it.
You should therefore have no qualms about alerting a possibly ambiguous bid since you are not conveying unauthorized information to your partner by doing so.
Larry Cohen in a 2015 article gives some interesting examples of possibly alertable bids.
With self-alerting, no need to keep track of ACBL rulings – just alert every not-so-obvious bid. Once you get used to self-alerting, you will find it becomes a natural part of the bidding process. Don’t forget that announcements, such as transfers, are also alertable.
Finally, if you’re unsure of the meaning of an opponent’s bid, click on it to elicit a response from the bidder.