I think that is a pretty standard and often needed tactic when starting a forum or community. A community is pretty binary; it's either dead or it isn't, so a it needs to be jumpstarted.
Yep, this is most communities are started. Either through literal fake users (sometimes set up by the staff, sometimes 'imported' from other sites) or by deals and exchanges with other communities (aka you use my site for a bit and I'll do the same on yours).
Not surprising at all that Reddit did the same thing.