I personally don't think it matters much at all, except in channels that specifically identify that way. However, I am male, hetero, cis, so its possible I'm just clueless.
Identity in general doesn't matter much on forums (as opposed to microblogs, like Twitter or Mastodon). Forums are focused on topics rather than people, and what is said is generally more important than who says it.
I’m male, hetero, and cis, too. I know there will be some things I’ll never fully understand because of that.
I try to keep things gender neutral (they, y’all). I know I’ll be wrong sometimes. When I’m corrected, I apologize and make sure I don’t repeat the mistake. There will be rare occasions where that’s not good enough for someone, but I look at that as more their issue than mine. I’m being sincere, and doing the best I can.
I'm not quite grasping the context you're asking the question, but I will say gender matters on Lemmy in the sense that I want full representation from all genders (and non-gender folk). The value of conversation here is derived from the many viewpoints that each of us bring. Without full representation, we'll be missing valuable inside and perspective if a specific gender (or non-gender) is missing.
Far less than on Reddit, but it still affects someone's experiences. e.g. just bc someone does not experience something daily does not mean that it never happens, but often a person in a minority status group has no choice to ignore such, while the privileged status person can.
In the context of the internet at large seeming to believe every user is male? I'd say that's still standard practice here even if it's not as prevalent and assumption as on other social media. How much that matters though is subjective.