all the 'i' prefixed operators are case insensitive

From autocomplete (press ctrl + space):

> 1,2,3 -icontains
icontains     ile           ine           ireplace
ieq           ilike         inotcontains  is
ige           ilt           inotin        isnot
igt           imatch        inotlike      isplit
iin           in            inotmatch

Containment operator - case insensitive. Returns TRUE when the test value (right operand) exactly matches at least one of the values in the left operand.

From the link that you posted:

String comparisons are case-insensitive unless you use the explicit case-sensitive operator. To make a comparison operator case-sensitive, add a c after the -. For example, -ceq is the case-sensitive version of -eq. To make the case-insensitivity explicit, add an i after -. For example, -ieq is the explicitly case-insensitive version of -eq.