> I’m not deeply familiar with what APIs are available for detecting extensions, but the fact that it scans for specific extensions sounds more like a product of an API limitation (i.e. no available getAllExtensions() or somesuch) vs. something inherently sinister

This seems like a really weird argument to make. The fact that the platform doesn't provide a privacy-violating API is not an extenuating circumstance. LinkedIn needed to work around this limitation, so they knew they're doing something sketchy.

For the record, I don't think they're being evil here, but the explanation is different: they're don't seem to be trying to fingerprint users as much as they're trying to detect specific "evil" extensions that do things LinkedIn doesn't want them to do on linkedin.com. I guess that's their prerogative (and it's the prerogative of browsers to take that away).