There isn't any public information on a particular "hdb opinions sort 1k 28" as this is simply not a normal HDB identifier. Having said that, HDB presents quite a few channels for feed-back. The most crucial system is from the "Publish to Us" e-opinions type within the HDB Web site. https://hdbfeedbackform1k2852963.bloggadores.com/36240473/hdb-feedback-form-1k-28