Will 100 km body impact with Sun produce burn for people on Earth? I think yes, but I need someone to look and check my reasoning:
If 100 km size body will fall on the Sun it would produce the flash 1000 times stronger than the Sun’s luminosity for 1 second, which would result in fires and skin burns for humans on day side of Earth. The calculation is just calculation of energy of impact, and many “ifs” are not accounted, which could weaken consequences or increase them.
(See some discussion here, but risk is not mentioned. Comet Hits The Sun
Such body could be from the family of Sun grazing comets which originate from Oort cloud. The risk is not widely recognized and it is just my idea. The basis for this calculation is following: Comets hit the Sun with speed of 600 km/s, and mass of 100 km size body (the comets of this size do exist) is $10^{18}$ kg, so the energy of impact is $3.6×10^{29}$ J, while Sun’s luminosity is $3×10^{26}$ W.
But most likely the energy will be released below sun’s photosphere, as its density is very low like 1 to 6000 of air. The resulting hot gas will flow up eventually but it will cooler and energy less concentrated. But even if it take several minutes, it still could produce burns on Earth.
From the original Comet Sun Collisions

DESTRUCTION AND OBSERVATIONAL SIGNATURES OF SUN-IMPACTING COMETS
  ABSTRACT
  The Astrophysical Journal, Volume 807, Number 2
Motivated by recent data on comets in the low corona, we discuss destruction of "Sun-impacting" comets in the dense lower atmosphere. Perihelion distances  and masses  g are required to reach such depths. Extending earlier work on planetary atmosphere impacts to solar conditions, we evaluate the mechanisms and distribution of nucleus mass and energy loss as functions of  and q, and of parameter . Q is thetotal specific energy for ablative mass-loss,  the bow-shock heat-transfer efficiency, and  the solar escape speed (619 km s−1). We discuss factors affecting Q and  and conclude that, for solar  is most likely <1 and solar-impactors mostly ablated before decelerating. Sun-impacting comets have energies  erg, (comparable to magnetic flares ~1029−33). This is released as a localized explosive airburst within a few scale heights  of the photosphere, depending weakly on  and X. For  and , a shallow incidence (e.g., polar ) Kreutz comet airburst occurs at atmospheric density —a height of 700 km (3.5 H) above the photosphere (where ). The airburst n scales as  (while height ) so n increases 1000 × (700 km deeper) for vertical entry. Such airbursts drive flare-like phenomena including prompt radiation, hot rising plumes, and photospheric ripples, the observability and diagnostic value of which we discuss

 A: The New Scientist link says:

The crash would unleash as much energy as a magnetic flare or coronal mass ejection, but over a much smaller area. “It’s like a bomb being released in the sun’s atmosphere,” Brown says. The momentum propelled by the comet could even make the sun ring like a bell with subsequent sun-quakes echoing through the solar atmosphere.

As far as I could see, from the Original Comet Sun Paper, this may not of the same order as previous CME's, but without digging into the paper to get energy figures, it's impossible to say. It's a very long, extremely dense and comprehensive paper which would require a lot of study, imo. 
The part that would require most attention by people with more experience than I imo, is a look at how the Earth's magnetic field would cope, compared to other CME events. We would have warning from SOHO,  I think before it vaporized,  so most  burns could be avoided, but I am not qualified to judge if it would become another Quebec level event,  or worse. 
