Comets are balls of ice and rocks. They aren’t made of plasma and they don’t burn.
We have so far visited or flown by more than a dozen comets and landed on at least one and found zero indications of ice. They have been bone dry, indistinguishable from the asteroids we’ve flown by and/or visited. The primary differences have been the comets have a far different electrical charge than the asteroids. . .
No one is claiming "plasma burns" or that they are "made of plasma." They create a plasma which enters a glow discharge state. When the electron start leaving the mass of the comet the strip material from that mass. This has been observed occurring in plasma laboratories and can be scaled infinitely as voltage and amperage increases. The surfaces of the comets we’ve visited show signs of such electron plasma sculpting. H2O seen in the spectra of the comae of comets is created by the interaction of ionic OH Hydroxyl radicals machined off the dry rocks by the charge plasma encountering the free Hydrogen ions in the Solar winds which create the Cometary tail and combine chemically to make new Water.
Dr. Jessica M Sunshine, director of the Spectographic team on the Deep Impact project in which a 670 pound space craft was collided with Comet Wild 2 was shocked at the purity of the water they were getting in a colimated spew from the impact point, just in a cone 3° off vertical from the perpendicular of the angle of the incoming projectile.
"It was as if we were seeing the water being created before our eyes," said Dr. Sunshine, although she would later buy into the orthodox theory that deep impact had punched through a surface crust into a deep cavern of pure H2O, water which orthodox theory claims must be converted to steam only by solar heating which must somehow raise the surrounding rock to above water’s boiling point, which then converts the water to high-pressure steam, which then finds its way through the rock to vent out to space to form the huge comae and tails of comets. . . all in volumes of space where the sun cannot bring shaded temperatures above 150° BELOW the freezing point of water, much less the ability to raise hundreds of millions of tons of rock, which everything below the cometary surface is by definition is SHADED (I.E. not in direct sunlight) to the vaporization point of that water! That has NEVER been demonstrated.
When the Deep Impact space craft hit Wild 2, the Electrical/Plasma Universe cosmologists made nineteen specific predictions of what would be observed which were counter to what orthodox cosmologists claimed would be observed. While the orthodox cosmologists were "surprised, stunned, and shocked" at what they observed, especially at finding less than 1/100th the amount of water they were expecting and the rocky surface, all nineteen of the predictions made by the Electric/Plasma Universe cosmologists were observed and fully confirmed their expectations.
If the test of any hypothesis or theory is how well it can predict future observations or the results of tests, or of those predictions to not be falsified, then the Electric/Plasma driven Universe Hypothesis is looking much better in this case than the gravity driven universe hypothesis whose adherents keep being "surprised, stunned, and shocked" by what Electric/Plasma Universe adherents have predicted will be observed and can explain why without invoking magical unseen, unfindable "dark matter" or "dark energy" to have their universe work.