Dahlia is the Nameless Bard reincarnated
My theory is growing... I think Venti got his friend back xD
Just screenshots of my tweets because I'm lazy. Disregard the birthdate tho, apparently in leaks characters always have that date until close to release.
General info:
We can obviously see that he and Venti are close, and very similar in personality and behavior. His leaked party animation even shows Dahlia winking like Venti always does, and that is also associated with having secrets
He holds the book Lost Prayer to the Sacred Winds. That might not mean much since that is basically a book about Barbatos, and he is the Herald... but I have for a long time thought that the unascended version of the book had a picture of the Nameless Bard instead, and called it the Nameless Bard book (people just wouldn't be able to distinguish it from Barbatos through appearance alone). Even seems to have a scarf like the bard, so above I include an old paintover I did about a year ago.
The lines from that book also sound a lot as if they were written by someone who expected to die - which might still apply to Barbatos. I'm not saying that the book was written by the bard - after all, it also mentions the oppression from the Aristocracy, and an Anemo Archon, which didn't exist while the bard was alive. But there are suspicious things there...
Dahlia's constellation is a symbol that is exclusively (I think) depicted in Decarabian's ruins. The closest alternative is Klee's clover.
Disregard the birthdate, we don't know that yet actually. I learned too late that leaks only update it close to the character release.
About Windblumes, the rebellion and flowers:
Other interesting stuff about Dahlia:
