For reference see topic on google group.

(...) Perhaps it could work like this:

Should Be Equal    ${string}    expected    ignore_case=True
Should Contain    ${list}    expected    ignore_case=True

• Must be backward compatible (default value as before)
• Must have Unit Tests expanded for new option.

Update by @pekkaklarck:

These keywords should get the new ignore_case argument:

• Should (Not) Be Equal
• Should (Not) Be Equal As Strings
• Should (Not) Start With
• Should (Not) End With
• Should (Not) Contain
• Should Contain X Times
• Should (Not) Contain Any (added in RF 3.0.1, see New Should Contain Any and Should Not Contain Any keywords #2120)
• Should (Not) Match