On sorting out letters: shapes and sound (induced) influence considerably the synesthete's perception of, say, a single alphabet letter.
Induced semantics and single linguism is often the foundation for specific grapheme-colour synesthesia aspects. These are wildly overturned when the individual is fluent in more than one language and has a solid mathematical background education. To simplify, the larger the pool of information the synethete has obtained the more variations of the same symbol he will perceive. Unfortunately, it is the basic, unexpanded perceptions that are considered suitable when developing so many so-called synesthesia tests.
On given personalities: strong personality traits are found in everything except in humans, among which such traits are often weak. Inanimated objects have each a different appearance, strength, weight and personality according to position, light, sound, space used and so on, even if similar or even identical to each other (for example, each cigarette in a packet is totally different from the next, coins in a wallet or cutlery in a drawer cause a riot when opened and viewed, or even just thought about without opening their container at all. Even each vertical iron bar in a sidewalk fence differs substancially from the next, every single wave in the sea, coloured particles that make up the air we breathe - from planets to molecules and atoms, everything differs from its equivalent, but there are always a few which tend to stand above the rest).
Automatic discernment focused onto a specific set of objects or area picks the 'best' elements, so to speak, reducing choice times. In practical terms, it would take hours to make a cup of coffee if this mechanism wasn't available. Regarding this, only lived-out experience teaches the synesthete what is understood by the general public (and accepted by general consensus) and what is not, or not even perceived, so as to ease the everyday blending among others.
Perfectionism over one or more activities is a trait that stands out in the synesthete, because of the above mentioned picking options.