IPs can be hidden but it's surprising that people often don't. Perhaps it's just the shit ones that get noticed.
It is pretty essential to look at the source of peculiar drive-by comment bombing, particularly when there are lots of comments saying similar things. I'm not sure whether this particular comment was part of a general strategy to make it look like there are real people who actually don't like the idea of affordable housing, or whether it was just some cunt of an estate agent posting on his own initiative, but odd "coincidences" like this are worth highlighting publicly; just like it might be worth mentioning that, say, comments from local residents approving of a new Tesco appearing on a local blog criticising it all seem to have IPs coming from a PR company hired by Tesco.