You did the right thing. You will not gain anything, if you are being honest, by having someone angry at you about this mower. Someone else will purchase it .
Having unhappy people only works if you live in an area that is so densely populated that you can just pileup unhappy people forever. I live in a rural area and chances are that these folks are my neighbors, know my neighbors, are related to my neighbors, work with my neighbors, are moving in next door , and will be my neighbors, or may just may want to get to know my neighbors. Keeping people happy always pays off, just don't let them screw you.
Oh and a short rant!
Why can't people put more information in their CL ads then,"Honda mower, runs great $200", or Kubota tractor, Great price always cared for" Please give me a few facts. HP? Year? Model #?
OK I'm done.