Had a real pleasure today; someone found a description of a League of Legends networking problem I wrote up a year ago and it gave him the clue to fix a problem he was having. (Long story short; specific actions in the game cause bursts of high network traffic, which can trigger lag or disconnects.)
I spend a lot of time writing up details of bugs and software problems. I do this partly for clarity, writing it up is a way to make sure I really understand the problem. I also do it so I can find my notes later in case I have a similar problem. And finally I put those descriptions online in case they help other people. And about once a year, they do!