When user wants to edit value of <f:selectItem> via Visual Editor he has to click on <f:selectItem> text tree times to select only item text not to select item text together with item button symbol. Whole item text gets selected. When user starts to type item text is deselected and first two characters of item text are replaced with typed characters. The rest of item text stays unchanged.
It works like this only for <f:selectItem> tag placed in <h:selectOneRadio> tag. It's not possible to edit <f:selectItem> value at all when it's placed in <h:selectManyCheckbox> tag.
When <f:selectItem> text is selected in Visual Editor cursor is put to this text and arrow keys are moving him but it's not possible to edit item text.

Test page is attached to this Jira: https://issues.jboss.org/browse/JBIDE-3860

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So the promlems are the following:
1) Three clicks to select the text in <f:selectItem>
2) Only 2 first characters are selected in the "itemLabel" attribute
3) Unable to select text in <f:selectItem> in <h:selectManyCheckbox>