On Wiki of Gold is a player-run wiki improvement project supported by ArenaNet with in-game gold that gets awarded to wiki editors for contributing to any article selected below. (You can read the Contribution Terms here. Note that all contributors to this project have to abide by these Contribution Terms and all contributing edits have to be done with a wiki account, meaning anonymous edits are disqualified.)
The GW2 Wiki is a fantastic resource, but while it's extremely useful, it's true that parts are lacking. So anet sponsors gold for people to update significantly underattended parts of the wiki, and contributors are encouraged to add any missing data (so long as it's supported by verifiable information).
Since the wiki itself is an entirely fan/player maintained project, it can't grow and improve without players actually going in and adding things they find missing. I've added missing dialogue myself in various places!
It's a really worthwhile project, and even if you're not doing it for gold, it's worthwhile to do to keep that information strong in the community!