Feedback from programs vary widely.
Some programs will not send any feedback post-interview regardless of correspondence to them. Some programs will only send perfunctory/polite feedback in reply to correspondence sent to them. Some programs will send out nice email to everyone who interviews.
Some programs will target individuals at the higher levels of their rank list and recruit with emails and phone calls. They do this in hopes that the more communication given, the more applicants will feel comfortable corresponding and asking for additional bits of information and the like so that they are comfortable ranking the program more highly.
I wouldn't make anything out of brief emails sent to you. It could just be courtesy. Multiple emails from multiple sources at a program is probably a hint they are strongly considering ranking you highly. But it doesn't matter. At the end of the day, you rank agnostically based on where you would like to go; some applicants try gaming the system to rank where they think they'll match, which serves absolutely no purpose and betrays an ignorance of the process.. The smarter programs will also rank agnostically based on who they would like to match at their program; some programs reportedly try gaming the system and rank folks they think are going to rank them highly. This serves them no purpose other than to have them not go below a certain point on their rank list. This does them no good, unless it's used a a metric within their university. I don't know of good programs that do this, though I've heard it happens at some places.
For what it's worth, I interviewed at about 12 places. I sent emails to each person that interviewed me, as well as the program director and program coordinator. I didn't do this in hopes it would have an impact on my ranking, I was just raised that this is the courteous thing to do when you interview for something. Of the 12 places, about 3/4 emailed back replies of some kind and 1/4 didn't. Three of the programs emailed me at a level I would consider recruiting, one of the three actually followed up with phone calls and periodic emails from different residents. The program I matched at, the first choice on my ROL, was one of the 1/4 of the places that did not follow up at all.