I think I’ll always prefer to maintain two accounts just for the flexibility, but if I could follow a stream of /c/ posts-only from my Mastodon, it would really simplify the process of sharing those posts to my mastodon folks.
Right now, unless I follow the firehose of an entire /c/, then sharing a post to Mastodon means I have to see it from my Lemmy account, copy the post link, rewrite the link to open on my Mastodon instance, open it, and then share it.
I think someone will add it to base Lemmy eventually, but I doubt it’s high priority. Might be a while.