I did a bunch of experiments today and ... thoroughly confused myself, so I wrote down a bunch of things and took screenshots.
Here's what I learned:
(I have more protocol info but ultimately this is the lived experience of working across different software systems, federation, and the actual client / front end web experiences that people interact through)
Paste Lemmy URLs
Various things "just work" by pasting URLs into the Mastodon web interface or the Mastodon mobile app.
Posting the link to this post https://lemmy.ca/post/606549 finds this post
Clicking on the user profile shows me a profile for Doctor_Pi@lemmy.ca, with one post displayed. Including a follow button
Only one post is shown, because that's all that's available on the local server right now. If I chose to follow Doctor_Pi's Lemmy account, I'd get all of their posts going forward. Both OPs (which has a link to the post on Lemmy.ca) as well as comments (which appear as replies).
Limited support on other clients
Other clients (Ivory on iOS) have extremely variable support. You can't usually paste in Lemmy URLs, but you can paste in Lemmy accounts and follow them, and then see posts going forward.
Please leave a comment of what does / doesn't work in your particular client.
Follow Lemmy users on Mastodon
Every Lemmy user can be followed on Mastodon. So, for example, my Lemmy account @boris@news.cosocial.ca. Paste that into the web interface of Mastodon or into the Mastodon native mobile app and you will find my Lemmy profile and can follow it.
Reply to a Lemmy post from Mastodon
If you reply to a Lemmy post using your Mastodon account, your reply will be posted as a comment. A user profile is created on the Lemmy instance.
I just did that with this very post, and it seems to have worked.
This is my boris@cosocial.ca Mastodon account, viewed through news.cosocial.ca as a local user profile. All of that info -- including the images -- are from my Mastodon profile.
The comment is technically originally on Lemmy.ca.
Create new OP post from Mastodon
You can create new OP posts directly from Mastodon. @-mention the group name, e.g. @vaneats@news.cosocial.ca.
I think with time, compatibility between different services will become better, so far with lemmy limited compatibility and kbin with full compatibility, we are going in a good direction
I'm also not sure the interface is quite right. There are maybe use cases where subscribing to a lemmy community or kbin magazine might make sense in Mastodon, but most of the time that feels like a weird use-case. It feels like I want to subscribe to my own feed of people who reply to me, then I could reply to them from Mastodon (except there's no real link between my identities, which is messy)
My wishlist would be to be able to link Mastodon accounts to Lemmy accounts, so the Lemmy system "knows" it's the same person. Including being able to edit the posts that come in from Mastodon, which right now is the biggest issue.
This post as an example, I was framing it as a Masto post, and it's pretty terrible on Lemmy. I'd focus on optimizing favourite/boost/comment from Mastodon as that is I think going to work best - comments don't need first class titles, links, and feature images.
For OPs, wouldn't it be amazing if I could DM some links and images and stuff, and then login to Lemmy/kbin and have it appear as a draft, and then publish it natively with rich text tools on the Lemmy/kbin side.
Subscribing via Mastodon works much better for me, even if I then go over and interact with my Lemmy account. I want both OPs and comments, and it's easy enough to put in a list or otherwise manage notifications from my clients. Micro-blog native vs Thread native people are going to differ in their opinions here :)
Yeah absolutely, plus there's lots of space for new entrants with different ideas for what a hybrid platform might look like. Some of them will surely be terrible but maybe there's a magical do-it-all solution that we just haven't imagined yet.
Not having to recreate the community from scratch makes it so much easier for technologies to emerge
I think kbin has a good aproach to this, a completely different tab that allows you to make posts in the mastodon format. This could also be the case on lemmy some point, however I would understand if lemmy users don't want this at all.