An approach I've seen work wonders is to begin with contradictions in a character's foundational premise. Instead of just a 'brave knight,' consider a knight plagued by chronic, debilitating fear who has meticulously trained their body to act despite it, their courage existing solely in the physical execution, never in their mind. This internal war becomes a fertile ground for roleplay. What happens when their meticulous control slips? How do they explain away their moments of paralysis? The unique element isn't the trait itself, but the specific, almost mechanical contradiction that drives their every action. From there, you can layer in a text-based roleplay hook: perhaps they communicate only through written notes or scrolls, having taken a vow of silence to hide a vocal stutter that emerges under stress, making every written exchange carry the weight of their hidden vulnerability.
Moving beyond the initial concept, the uniqueness blossoms in how the character's specific psychology filters their interactions with the world. Their 'voice' in text shouldn't just be a collection of quirks, but a direct outflow of their core contradiction. Using the fearful knight, their writing might be excessively formal and precise, an attempt to impose order on a chaotic internal state. They might over-explain tactics in messages, betraying a need for absolute control, or they might avoid certain emotional words altogether. In a roleplay scenario, a simple prompt like 'the tavern is noisy and crowded' could be interpreted by them as a logistical threat assessment, detailing exit routes and potential hazards in their response, while another character might focus on the smell of ale or a minstrel's song.
Finally, embed the potential for evolution directly into the character's text-based interactions. The uniqueness shouldn't be a static statue. Perhaps the knight's roleplay arc involves their written communications slowly becoming less formal, introducing a hesitant typo or a fragmented sentence as they begin to trust their companion. Maybe they start to use metaphorical language for the first time, comparing their fear to 'a cold forge' rather than listing its tactical disadvantages. The roleplay ideas stem from testing these boundaries—presenting them with situations that force a choice between their old, safe text patterns and a new, risky mode of expression. That moment where they finally send a message that says simply, 'I am afraid,' without any qualifying data, is where a unique character becomes a memorable one, all through the medium of typed words on a screen.