So, my luck finally ran out and I accidentally broke my phone. I figure it was about time since my streak has been going since I got my first nokia brick back in the day, which doesn't really count as they were nigh indestructible anyway.
But that has meant an opportunity to find new bugs and other issues.
I'm now using a device running Android 9.0 (Pie) and it's currently using Chrome 75.0.3770.143. I also tested this particular issue in Firefox 68.0.
Bug Report: Chrome for Android doesn't play quite right with the "post message" screen.
When you first enter the page everything is fine. Then when you press in the text box and begin entering text, the box expands slightly in size and covers most of the "preview/delay post" and "post message" buttons.
As seen here:
https://i.imgur.com/moyz7v4.jpg
You can type normally. The buttons themselves still work, if you press the "preview" button either the small bit that's still showing or the area of the text entry box where the button is, it will work as intended. It does not work correctly if you have typed enough that the text entry area that covers the button now has text in it. In that case pressing the screen just puts the cursor where you pressed, you must instead press the small bit of button poking out the bottom to make it work.
Once you have reached the "preview" screen the text box behaves normally, and the buttons are fully accessible. Entering/deleting/etc text in the box does not seem to trigger the issue, nor does subsequent presses of the "preview" button.
When I tried to replicate this issue in Firefox I could not. Of the two browsers only Chrome seems to have this issue.
I was running an old Windows Mobile 10 handset for the past few weeks in the interim, so I don't know if it's strictly a software/browser issue or something due to one of the updates to the site made in that time period.