Free plan features:

• Create new ticket based on current one
• Auto-fill from last comment
• Creates link between tickets
• Comment on original ticket
• Append CCs to new ticket
• Close ticket directly
• Too large attachment handling

Premium plan includes all features from the Free plan, plus:

• Pick comments, assignee & requester for new ticket
• Custom fields support
• Add attachments
• Optionally add tags to new ticket
• Designate default form
• Allow administrator to disable close ticket feature