A recent answer presented the following ruling from Dragon Magazine 371, page 9 (emphasis added):
If you choose multiple heritage feats (or feats that similarly modify at-will powers), you choose which feat modifies the power for the purposes of resolving the attack with the power.
I don’t have the issue myself, but this ruling appears to be a broad ruling that lays down a fundamental rule for all games of D&D 4e. However, a search of the online compendium doesn’t turn up this same rule, and I haven’t found this rule reflected in either the Rules Compendium or the player’s handbooks I own.
This is startling for me, because I expect these rulings to be strictly the domain of published manuals, whilst it’s the role of Dragon Magazine to simply produce extra content. It’s even a little concerning, since Dragon Magazine has produced some of the game's most headscratch-inducing material, like feats, items and powers that are strangely worded, or which make poor (or incorrect) use of D&D 4e conventions such as the power block format. Their QA and editing processes seem to not be as rigorous as those applied to the manuals.
That all said: if a Dragon (or Dungeon) Magazine article lays down a general rule that can apply to all games of D&D 4e (including those not even using magazine content), and it’s never reflected in a published manual, is that an official rule we as players should respect as such and make efforts to play with?