• The controls are no longer listed backwards in the source.
• I put the br creation in the loop (as you suggested).
• I replaced the hardcoded 2 with arr.length.

function createInput(name, visual, callback) {
    var input = hue_create_radio(name, callback);
    var text  = document.createTextNode(visual);
    return [ input, text ];
}

var to_insert = [
    createInput('code',     'Add code tags',        hue_set_code),
    createInput('readmore', 'Add readmore tags',    hue_set_readmore),
    createInput('retitle',  'Retitle',              hue_set_retitle),
    createInput('reap',     'Reap duplicate/empty', hue_set_reap),
    createInput('other',    'Other',                hue_set_other),
];

form.insertBefore(
    document.createElement('br'),
    checkbox.nextSibling
);

for (var i=to_insert.length; i--; ) {
    var arr = to_insert[i];
    for (var j=arr.length; j--; ) {
        form.insertBefore(arr[j], checkbox.nextSibling);
    }

    form.insertBefore(
        document.createElement('br'),
        checkbox.nextSibling
    );
}
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