Lemmy is like Reddit, which is used a lot to ask questions and get help. But StackOverflow fills a different niche, it's meant to be useful to as many people as possible and stay up to date. This is why

• there's a distinction between "comments" and "answers" (comments can be used to request additional information, and for meta discussion)
• both questions and answers can be modified by other users, for example to
  • add more information, or remove unnecessary details
  • correct outdated information
  • fix typos and formatting
  • rephrase sentences that are confusing
• a question can be closed as duplicate, so people always find the oldest thread of the question with the best/most detailed answers
• before submitting a question, you get a list of related questions to avoid creating a duplicate question
• questions have tags, making them easier to search for