From the app's about section:
Stack Exchange Android App Version 1.0.83
This is the beta version of the official Stack Exchange Android app.
I'm on Android 6.0.1, Nexus 5.
Creating block quotes can lose text, and doesn't insert Markdown the same way the browser editor does:
Inserting screenshots messes up pre-existing links/images (usually the first two):
Note that I manually edited the Markdown for each image so that it pointed to the large thumbnail and linked to the original. I had to do that since the 1080×1920 screenshots are way too large on a desktop. I think there's already a feature request for that somewhere here.
Selecting text within a paragraph, leaving out the leading words in the first line and trailing words in the second line creates a code block, instead of inline (backtick-surrounded) code span:
This also happens when the selection is in the same line, but I'm not sure how reproducible it is. Sometimes even a single word can become a code block, sometimes multiple-word selections are enclosed in backticks.
And, yes, each time I inserted these screenshots, the first image's Markdown and image link were altered. So, the first image became just a link that actually points to one of the later images. Since the original link to the first image is now lost as the editor replaced them with the link to a later one, I had to upload it again. (In the process, the second image's link numbers were altered, and the entire set of links at the bottom got their numbers decreased, so that the numbers were mismatched. After I noticed the links being changed, I starting copying the links before uploading new images, so I was able to quickly fix that.)
In this context, an undo button becomes necessary. Markdown becoming messed up as with the code blocks can be lived with, loss of data like in the block quote and image uploading situation is untenable. I've been observing the image upload and code formatting bugs for some time now (at least a month - my last couple of bug reports about the app also gave me trouble uploading images).
Just for kicks, here's one I screenshot I took while making my last bug report, which I just noticed I had taken and now have uploaded via the browser: