Caps, and the Crossbar I
Comics letter in capitals, and the one letter that bends the rule — for a reason

The convention that holds
Open almost any hand-lettered comic and the text is set in capitals. This is not shouting — it is a practical inheritance from an era when reproduction was poor and a lowercase letter at small size could bleed into illegibility. A capital alphabet gives every character a clear, upright silhouette. Distinctions hold under pressure: at nine points on newsprint, an n and an m can merge; their capitals remain separate.
Within that all-caps convention one rule operates so quietly that most readers never notice it, even as they rely on it constantly. The capital I takes a crossbar — a serif above and below the stem — only when it stands alone as the first-person singular pronoun. Everywhere else, in words like INSIDE or FRIGHTENED, the I is a plain vertical stroke, no serifs, nothing to distinguish it from any other vertical stroke in a letter's structure.
The reason is disambiguation. In a caps-only alphabet the plain I is identical to a lowercase l rendered large, and dangerously close to the numeral 1. When the word I appears mid-sentence surrounded by other capitals, context usually resolves it. But as a single isolated character — I KNOW, I CAN'T — the bare vertical is just a line. The crossbar makes it unmistakably a word. It gives the reader a clear signal without slowing the line.

The discipline is to apply that crossbar only where it does grammatical work. A letterer who crossbars every I in every word produces a texture that is fussy and harder to scan. One who drops the crossbar from the pronoun makes a sentence stumble. The rule is binary: pronoun gets serifs, all other uses get the plain stem.
This is lettering as structural decision-making — which is the only kind that matters. The crossbar on the pronoun I is not ornament. It is punctuation in the typographic sense: a mark whose sole job is to prevent a reading error. The convention holds because no better solution has been found. When you next read a comic and sail past I NEVER KNEW, notice that you read it instantly and without effort. The crossbar did that.
