Hi tnghome
I find this thread very informative and relevant to my case too.
We also found our 5room flat from PropertyGuru.com and at the same time, we offered to let this seller agent to sell our current flat (contra transaction). Like you, I was thinking whether to give that 1% buyer commission to the agent since we already let her sell our flat and earn 2% here.
After calling the Institute of Estate Agents and HDB hotline, I came to the conclusion that we are not liable to pay the buyer comm as long as we did not sign the buyer commission agreement. Even if you have signed the agreement, my agent told me that it's always negotiable (say around 0.5%), depending on your assessment of the agent's service.
Our 1st HDB appointment is in June, but I told the agent that we will not pay any commission until the completion date, she's agreeable to that now. Hope everyone can learn from our experience and dun fall into the agents' traps.