I wonder if it would be possible to put more priority on this feature?
As much as I have read of the problems of implementing the feature, this doesn’t seem to be possible to do as a community plugin, so the only option is for obsidian application to support first line indentation.
To be clear, I would expect the indentation to appear both in preview and in edit mode. It’s such a basic feature of text editing that I’m amazed obsidian doesn’t have it.
It’s like your favorite text editor can do everything you wish, but can’t add a space. Like building a rocket, but don’t have fuel.
The way I would expect this feature to work is that where ever I have pressed the enter-key, it would add an indentation, which can be changed from settings. I don’t expect any html tags to be added by the user.
If Obsidian would have this feature I would be able to delete other writing applications that I use (like Storyist) and just use Obsidian instead. This one missing feature makes it impossible to delete Storyist.
I hope the developers of Obsidian would see the value of this feature. Everything else is already possible with Obsidian. 
Cheers, Petri J