"Do you think that a BD is a star that failed, or should it be classified as a different object all together?"

I think in a sense, this is a stylistic question. You could just as easily
say that the sun is an incredably successful brown dwarf.

If you want to center your classification upon stars like the sun, then
I think it's safe to say that brown dwarfs, have very little in common with the sun in it's evolved form.

It's all just syntax....

"It's not I who stated that a black dwarf would be visible, the
argument I worte was paraphrased from the source I listed,
though I do believe that an object hot enough to begin Deuterium burning (~1 million degrees) would be visible in white light, though
it's absolute magnitude would be substantially positive, even at it's brightest."

Ummmm, well the surface temperature of stars (in this case including
BD) is what we measure and how they are classified by spectra.
Sol is about 5,000K. Brown Dwarfs have a surface temperature that is anywhere from 1,600 to 2,200 Kelvin. If they were hotter, they
wouldn't be Brown, they'd be red or yellow or white or ........

If your not already, familiarize yourself with the HR (Hertzsprung-Russel)
diagram and black body radiation, specifically, how spectra scales with temperature. This may help resolve some of your misconceptions.