If you look at HN ranking trackers then you'll see there are definitely artificial adjustments to the rankings of articles. Mostly that is downwards but sometimes upwards too.
HN is mostly fair, but don't trick yourself into believing it is completely fair.
There are factors beyond naive weightings, as well. I remember reading somewhere that if a thread becomes too heated or turns into a flamewar, the mods have the ability to suppress it in the rankings artificially to let it cool off. That functionality makes sense, but wouldn't be easily identified in a third-party tracker.
A lot of comments here seem to be assigning moderation as bias.
HN is mostly fair, but don't trick yourself into believing it is completely fair.