Not to defend Parterre Box, which has a big number of morons sporting coy names, it has some teenagers posting, and many of the 'commentators' range from early twenties to thirty five, that is younger than the average 'opera audience' (NEA has found the larger segment of this small and shrinking audience to be between forty and fifty five, younger than the swells at DL assume, though I guess for the brain trust here, forty five is impossibly decrepit).
A lot of the above is just confusing but then I guess opera queendom is for those outside, with loosely used and far from precise terms like 'spinto' and 'dramatic' and 'coloratura mezzo'.
Lyric is the base category for voices. Most roles can be sung even in a big house by a well projected lyric voice, though different singers have different strengths and specialties, some are 'lighter', some 'heavier' than others.
Radvanovksy is a 'spinto', a lyric who has built for volume and thrust. Many big voices are essentially spinto voices, designed for size, and sometimes there is forcing, and pitch problems result.
A 'dramatic' voice is now really rare but is the largest operatic voice, ideally, huge and in the Italian Rep with an exciting top (Corelli, Del Monaco, Tucker after 1955 or so would qualify), Vickers and James King in German Rep. Nilsson and Gwyneth Jones were probably the last true dramatic sopranos, enormous voices, though Jones (as usual in opera loved and hated in about equal doses) had technical trouble and wobbled. Marton had a very big voice but I'd categorize her as a spinto with some dramatic qualities -- and so you see -- both opinions and quibbles take a place in all this.
Into the 1900s most singers could execute coloratura with skill and ease, including mezzo sopranos (a somewhat hedged category since earlier there were contraltos, the deepest female voice, and then sopranos, and many iconic 'mezzo' roles were originally sung by sopranos, Wagner's Brangaene, Ortrud, Strauss' Octavian and Composer, Mozart's Cherubino for example, and a role that became the property of 'coloratura sopranos', Rosina in the Barber of Seville was originally a contralto role as were most leading roles in Rossini).
However Verdi roles like Amneris and Azucena needed easy high notes and forced a 'new' category, mezzo, dramatic or lyric). S. Blythe is naturally a wonderful contralto, like many such the higher notes are a problem.
It was only in the 1920's that there began to be this idea of a 'coloratura mezzo', a mezzo with a lighter timbre but still darker than a soprano who could execute coloratura (Supervia was the first famous one, Bartoli follows in her footsteps, Horne has a bigger voice than either one suspects -- Supervia died in the '30's so no one alive heard her but Horne still 'specialized' in Rossini and other 'bel canto' composers, doing less well in standard mezzo roles like Amneris, though she sang it now and then).