For some reason, I no longer have the 
button at the bottom-right of the composer anymore on mobile? So I can no longer see previews of the post I’m writing. Is this intentional or accidental? Thanks.
Thats intentional, I should make a topic for it maybe.
You still can by using the markdown/rte toggle.
Brought this up a few days ago:
I noticed that, but in my experience the wysiwyg editor frequently breaks markdown, so I don’t see how that’s a valid option. Unless all the issues I had with it earlier this year have now been fixed.
the other option is to turn your mobile phone sideways (landscape) and see the previewer in wider viewport
It would be interesting to know if this is the case or not. Will you report back on what problem(s) you (still) experience?
I won’t have time for a few days, but I’ll explore a bit later this week and get back to you.
Open source community at its best: for those arriving here to want to ask for it back, a TC is already made
Thanks for linking it here!
I’m still curious to hear from people why they’d want the preview button back. A theme component only reaches forums whose admins go looking for a solution and install it - it doesn’t cover everyone who misses the button on forums they don’t manage themselves. So feedback with actual reasons is still valuable: it’s the only way to get a sense of whether this affects a handful of forums that are happy with a component, or whether the demand is broad enough that it belongs back in core.