I believe the rule, if adopted, will be very narrowly aimed at overtly direct acts of taunting an opponent during a scoring play. (Keep in mind that taunting otherwise is a generally applied unsportsmanlike conduct penalty.)
We all can thank Seahawks dimwit Golden Tate for making this proposed rule adjustment topical, although the antics of players like our own Logan Ryan probably have contributed. I happen to believe taunting has no place in pro football and, if allowed to go unchecked, does more harm to "the integrity of the game" than this proposed rule.
That being said (and after sleeping on it) I agree with those who fear the rule might be too far open to officials' subjective interpretation with so much at stake on a scoring play. This leaves the question of whether some cases of taunting are "worse" than others, which the proposed rule implies. I don't know what the answer might be aside from leaving the taunting penalty as is and addressing the issue further by fining perpetrators and/or ejecting them from the game.
I'm afraid I disagree with everything above, except the bolded part. If anything, the refs have repeatedly affirmed the fact that there are far TOO many vague and subjective rules within the NFL rulebook. Rules that do nothing to make the game fair, but only generate frustration among players and fans alike.
A good rule (in any system) is meant to be concise and clear as daylight...one which can be agreed upon by amateurs and experts alike. But of course, the NFL retains a plethora of 'grey' rules, because the controversy they create are good for ratings...that's simply the NFL's modus operandi.
Also, what's the need for a new taunting penalty when we already have unsportsmanlike conduct? The only difference seems to be that the taunting rules will give NFL the ability to negate a score. Now nullifying a TD because of holding or DPI makes sense, because the rationale is that the infraction enabled the outcome in the first place. But taking away a TD, for taunting, makes absolutely no sense whatsoever, is egregiously unfair to the scoring team, and will only worsen the already soiled competitiveness of the game.
If the NFL is fair and honest, they should enforce taunting as an ejection, suspension, or player+team fine. All of these would affect the team as well, which takes care of the argument that the team owns part of the responsibility. But taking away a TD...yeah, you'll start seeing Ellis Hobbes DPI-esque plays on a weekly basis.