sincere

is incommunicable because it becomes insincere through Communication.

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sincere | BrE s(ɪ)nˈsɪə, AmE sɪnˈsɪr | adjective sincerer | sɪnˈsɪərə(r) | sincerest | sɪnˈsɪərɪst | aufrichtig; herzlich ‹Grüße, Glückwünsche usw.›; wahr ‹Freund›