Sadly no video platform will ever stand up to yt without creators. Odysee is the closest and thats only because youtube bans decenting opinion about topics

Will this be linked in the sidebar of the Lemmy.ml community or set as a pinned post?___

Not that i am aware of. Howerlver users are always @user@domain from what i have seen and you can always copy a link into your instance search box and get the resulting profile post, comment, whatever to surface

They all talk to each other.

From my mastodon account i can:

• follow sublemmys
• follow lemmy users
• comment on lemmy posts
• comment on lemmy comments
• share lemmy posts
• share lemmy comments

From my lemmy account i can:

• follow mastodon users
• comment on mastodon users posts
• comment on mastodon users comments
• crosspost mastodon users posts to sublemmys

While i have never used kbin i have no doubt that it can do everything listed above.

Really the fediverse is a “choose your own interface” kinda place. Do you understand reddit UI best? Use lemmy. Does twitter UI make sense to you? Use mastodon. Do you like both? Use both for different reasons. Either way you can interact with anyone, using anything, anywhere that uses activitypub and anyone, from anywhere, using anything supporting activitypub can interact with you. That is the whole point. Get rid of the silo social media so you never have to lose your social graph again because you moved to a new service they are not on

Headsets, no. They weigh to much and every damn gram counts. Glasses, sure