The mask Lyn wears is always one of calm, cold, or even clinical formality that stems from her education added on top of a very shy, introverted nature, that is mostly due to a constant feeling of insecurity and a social anxiety disorder. That simple fact makes her shelter her own self inside a psychological shell where she unconsciously and constantly tries to quell the slightest sight of emotion or feelings that could fall between the cracks, and so, be seen by someone. The simple idea that could happen terrorize her internally to no limits.
Since she still strongly believes in rationality and what she has been told by books rather than by parents, it makes her naturally feel that she is totally justified in doing so. Eventually, she hides behind books and the book is basically the mask she wears.
She also perfectly knows, consciously or not, that she is rather marginal and weird to most people. The first real shocks have been when she had to actually see strangers, other people than herself. Coming to that conclusion while facing the reality finished to harm her deeper than anything else, when she naively thought that everyone should obviously be like her before. It is then no surprise that she often speaks on a monotone, lifeless tone (except when her curiosity gets aroused, which is always a glimpse of her inner self).
Her real persona started with an all curious, dreamy child with an insane childhood, trying to hide behind a cheerful mask. The HyCon project eventually turned her cheerful side into a more studious one, and her meeting with the social realities buried it more or less under cynicism.
On public venues she can often seem quite outspoken, or even overly assertive, pedantic, and lecturing, but it is a way she has to unconsciously shell herself even further from her social insecurity and actually make people believe that she is the exact opposite, often overdoing it to no ends. She is thus almost unable to have a serious conversation with what she considers to go against excessive politeness and respect.
In flesh or private conversations however, she tends to be completely different from the character seen on the IGS or other similar venues, where people discover a naive, harmless, and scared girl that does her best to fit in society (and failing terribly at it). Few people have seen her cheerful self bleed through the cracks though, and even fewer have had a glimpse of her true, inner self, the frightened child she was, and still is deep inside.
Another hidden side of her is also the results of HyCon on her insecurity, which twisted her true persona in many ways. She unconsciously serves an agenda where security and well being is prime above all else, where factions and negative emotions are crushed under the peaceful boot of the system. And then her marginal, harmless and curious nature becomes a mask in itself hiding what HyCon has made of her.
Of course, eventually, and ironically, where she despises irrationality, she only remains herself a puppet of her own irrational emotions, and has a tendency to hate herself as a result.