Jira does this better, but is still weird with their text formatting. There are two different kinds of input fields, one of them accepts markdown, the other one some other kind of markup language. Copying some formatted text from one of the inputs to the other doesn't work because of this.
If you are in the new editor for Confluence Cloud (i.e. the editor based on ProseMirror rather than TinyMCE), you can sometimes get it to do "the right thing" of converting pasted markdown to formatted text by copying from a different text editor. For example, for me copying from windows notepad always does the right thing, but copying from vscode doesn't.
Make one mistake, you're good. Make two, tough luck, you can only undo once. Accidentally select some (or all) text and type over it then somewhere else? Today's really not your day. It's actually worse than textboxes in this respect.
This happened to me more times than I'd like to admit before I knew better.
It's actually one of the best on Windows, because if you leave your computer for a moment and it randomly decides to restart to install a Windows Update, often a notepad with unsaved changes will block it from restarting, whilst unsaved work elsewhere won't.
As far as confluence, or just about every web tool I've used that has text areas (slack, etc) - I really wish that would be handled over to the browser.
This leaves them very vulnerable to another company taking their market share, as soon as they create something better that is extensible enough to get management signoff. I know a lot of companies have tried and failed here, but someone's going to eventually do it.
Every issue type is configured with its associated issue-create screen and that screen has its fields. When you change the issue type during issue creation you're replacing one set of fields with another which results in the information loss you experienced. This just doesn't affect the description field, but all other system fields and custom fields.
That "Issue Type" dropdown box is what I changed a value for and it cleared the description below it (also seen in the screenshot).
Our set up might be pretty basic because the A to B from my original comment was "New Feature" to "Improvement" which is included in that screenshot.
saved my sanity more than once regarding lost jira inputs
A few days ago[0] I was writing a Jira ticket after hitting the "Create" button and I wrote the description (the body of the ticket) for ~30 minutes. I switched the ticket type from A to B (no epics involved) and it wiped out the entire description. All I did was select a different item in a select drop down box provided by the form's UI.
There was no warning it would clear the description and no draft saved. I lost 30 minutes of work.
I normally manually copy textareas every few minutes on any Atlassian page because I don't trust their site (to be fair I do this for most sites too) but in the above case I had just copied a link reference which overwrote my clipboard. At the time I also didn't have a multi-clipboard tool installed since it was using a company issued machine that I don't have tricked out yet.
[0]: https://twitter.com/nickjanetakis/status/1540353527859466246