I made a code change and now for both Group discussions and Forum discussions, you will get additional options when composing a post. You'll get the initial editor view that has an "attach file" button, but now you'll see a grey box with a little book icon for writing your post. Click that book and you'll be in a text editor window where you can compose your post and it has options such as bold or italic text, adding a link, and also embedding an image - which I think is what you were hoping for- to embed an image right into a post so it shows within the post rather than simply attaching it. Once you are done composing, you click the Back arrow and you'll get back to the grey box where you can then see your composed text, attach a file if you want, and click to publish your post.
I hope that people will like this change- it creates a small extra step to go to the Compose editor, but you get several useful added options this way. It's not got as many cool options as the text editor on our main desktop version, but it's now not quite as 'stripped down' in functions when posting from your phone (which i saw you were, from your screenshot).
Give it a try. Might take a few times to get the hang of it, but I think it's worth having this way.
Those irritated by grain of sand best avoid beach.
-Strumelia proverb c.1990