I'm the author of this paper and I absolutely agree. If you keep identifiers, simply blurring the location isn't enough to address the risks of re-identification (https://twitter.com/yvesalexandre/status/524219573650722817).
Re-identification is a very different risk than the one considered by the UC Santa Barbara researchers in Wang, Gang, et al. "Whispers in the Dark: Analysis of an Anonymous Social Network." (2014).