Nope. I don't think it can be done if you used the guest account to post a message.
You would need to make a new post in that same thread, to clarify what was meant - if it's really worth doing.
Paul
Win 10 Home 64-bit (w/admin rights) - Zone Alarm Pro Firewall, MalwareBytes Premium A/V, Cyberfox, Thunderbird
Sandboxie user since March 2007