The information provided in the Description and Biography is IC information. The Last Login for sure is OOC. Infofield 1 is IC information also. The Profile itself I treat as an OOC gathering of data from a character-useability standpoint (IE: No, my character cannot use that information automatically/absolutely ICly.). IMO Profile information should only be used if it makes reasonable sense for your character to know it (including reasonably be able to find that information out).
Holocron is much closer to an IC database of IC information, so you'll more commonly see people referencing Holocron information as rote Canon and publicly knowable. Care should be taken as the Holocron isn't necessarily "True" Canon just like the GNS isn't necessarily "True" Canon. Holocron articles can be complete lies, whereas the Profile is closer to an RPG Character Sheet Bio to help other Players understand one's character.
(Edit: restructured/rephrased paragraphs for more sense)
Darkness can be seen as a local government unaffiliated to any faction. Darkness planets cannot have player built facilities on them (except in some really rare circumstances) nor can anyone take control of them. Planets owned by darkness are usually racial planets or planets intended for quests (which I believe has its own separate owner called quests instead of darkness).
Darkness is just a really old name for this version of the Combine's website/client. We've gone through several clients, including downloadable ones like ICIS, but we moved to this website version over a decade ago and for some reason referred to it as Darkness.