It is probably coming from a hotel rep and not Hilton corporate.

I had a stay this summer at the O'Hare Hilton and left a very good review and gave five stars. I commented the only complaint I had was that there was a was rag on the shower shelf from a prior guest housekeeping missed. Received a PM from someone at the hotel wanting my room number and dates. Sounds like they have had some housekeeping complaints and wanted to check into it, even though I thought it was a very minor thing.

I've left complaints a couple times about non-Hilton establishments on TA and have gotten private messages. I think it's a good sign that a business is responding and taking action.