relatedTo 'and' with 'or' Is the following possible:

{% set issue = craft.entries(section: 'issues', slug: 'october-2014').first() %}

{% set categoryOne = craft.categories({ group: 'articles', slug: 'category-slug-one'}) %}
{% set categoryTwo = craft.categories({ group: 'articles', slug: 'category-slug-two'}) %}
{% set categoryThree = craft.categories({ group: 'articles', slug: 'category-slug-three'}) %}

{% for entry in craft.entries({
    section: 'articles',
    relatedTo: ['and',
        ['or',
            { targetElement: categoryOne },
            { targetElement: categoryTwo },
            { targetElement: categoryThree }
        ],
        { targetElement: issue }
    ]
}) %}

    {{ entry.title }}

{% endfor %}


Attempting to return articles associated with a specific issue from within one of three specific categories.

It appears the parseRelationParam function looks at the first array element to determine the operator but I'm hoping someone has a solution.
You can simply get all the relevant categories at once and combine your relatedTo parameters with a single and operator:

{% set issue = craft.entries({ section: 'issues', slug: 'october-2014' }).first() %}
{% set categories = craft.categories({ group: 'articles', slug: 'category-slug-one, category-slug-two, category-slug-three' }) %}

{% set entries = craft.entries({
    section: 'articles',
    relatedTo: [
        'and',
        { targetElement: issue },
        { targetElement: categories }
    ]
}) %}