help with editing issues JIRA REST API

[David Koh]

When I try to edit issues, I can edit assignee, description, summary, issue type, and priority. However, I cannot edit status, comments, or projects.

I found that maybe you can edit statuses via editing transitions. What is the difference between status and transition? 

If an issue is under Project A, is there nothing I can do to move the issue from Project A to Project B?

[Nic Brough -Adaptavist-]

Status, project and comments are not fields.

Status can only be changed by moving the issue through the workflow.

Comments have their own API calls, as they're not fields.  Have a look at the REST API calls for api/2/issue/<issue>/comment

Changing the project (and in fact, issue type, if the source and target issue types are configured differently) requires a "move" action.  Last time I looked at the REST API, this was not available.  I suspect because it's a complex task that requires a load of checks for data compatibility.