I can understand both strands of opinion. However, a sense of fair play suggests that a customer should first contact a vendor if there is a problem with goods or services that had been purchased, but only go public should they not receive a reasonable or satisfactory outcome. In the case of model rail supplies, one would contact the retail outlet who supplied the goods rather than the wholesaler or manufacturer, who may in turn may take it up with their supply chain.
It is quite another matter to complain publically about goods or services that may not have even been purchased by the complainant, and one would have to be very careful not to defame the good name of a business or person on mere internet hearsay. Fair and objective comment is however valid. Talking quietly behind the scenes more often than not, but not always, tends to resolve issues better then publicity on the internet. Yet pointing out any truth in a fair and reasonable manner is valid.
On the other hand, one doesn't want to harm the goose who normally lays the golden eggs just because one didn't hatch as well as others. Even if the goose decides enough eggs have been laid over the years, this customer is very grateful for the superb eggs in the past.