Drawing the letter I in professor layton?

The trick is to draw letters with multiple strokes quickly (don't try to be precise)

If the game sees you quickly add more strokes then it changes the letter that it may have initially shown

When drawing an "i", draw the line then quickly add the dot

If you're still having trouble, try drawing the line upwards so there's less space to move the stylus between the line and the dot

Naturally, make sure you've selected the lower case option

Incidentally, the name entered at the start of the game is really only there to name the save file slots (you're not naming a character or anything) so you could just use your initials or something