Comments is not a field, it's an optional place to enter a comment about what the user is doing. You can remove it by removing the user's ability to comment on issues, but generally, don't bother, it's far too useful.
The other fields are far more simple - for each transition, look at the "transition screen" it uses. You can edit the workflow and change these (even remove them for instant transitions) to use any screen you want. And you can put whatever fields you want on any of these screens.
There is an important exception to that - do NOT remove the resolution field from transitions going from an "open" status to a "closed" type status. You really do want it to set a resolution. If you're desperate to remove resolution, then you need to set it in post-functions instead.
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