I'm really confused, but it seems to be the convention that there is no "I":
The rows are numbered 1 to 19...
I'm really confused, but it seems to be the convention that there is no "I":
The rows are numbered 1 to 19...
Zeiss isn't completely correct, this is actually the less common reason for omitting the I. The more common reason why I is often omitted where it would normally be expected between H and J is because in sans serif fonts the uppercase "I" is completely identical to the lowercase "l" (L). In a go board if you see a move noted in uppercase as I6 or lowercase as l6 without any other context you could not tell the difference in these fonts.
Confusion between a letter and a number would be much less common, since the letter in go is given first and the number is given second for hybrid notation, but confusion between L and I would be possible and is avoided by not including an I at all, thus guaranteeing that L and l both refer to the L column.
(for anyone with an interest in typography, this was actually intentional, allowing the lowercase l to be used in place of an uppercase I made it easier on the typesetters, they had more available of both that way and had less different symbols to worry about. Same way p and d or b and q are the same just rotated)
In most cases, where "I" is omitted between "H" and "J", it's to avoid confusion with number "1". It's also common to omit the letter "O" for the same reason (confusion with number "0", more of a problem in some fonts than others).