If we're talking about posts in !newcommunities, then I'm 100% on board! I think that would be really helpful.
If we're talking about lemmy.world-wide across all communities, then I respectfully oppose this suggestion. I can easily see the community name underneath the title of a post. Adding the community name will cause communities to have pages and pages of posts that all start with the community name. Furthermore, if we ever get post tags, they will take up even more space and overwhelm the reader.
[meta] Can We Please Include The Community Name In The Title?
Title