Possible Clues:

• Texter's "then again"
• Texter's "That said ..."
• Letters before a fresh take
• Short ''Speaking of changing the subject . . .''
• Tweeter's 'alternatively'
• Text-writer's segue
• Texter's "Although ... "
• 'But at the same time . . .' for short
• Conversely, in a text
• Texter's rebuttal