Never say never
However, high only hands have amazingly little equity even in quite large multiway pots, in MANY cases. Good high hands almost always have equity to see a flop, because of the implied odds and the ease of folding if the miss, obviously you know that. However, they're rarely really an equity favourite, or perhaps I should say LIKELY to be enough of an equity favourite (given you don't know what your opposition holds) to make it significantly +EV to raise them up. There are, I guess, always exceptions - you rightly point out here that your hand is PROBABLY a slight money favourite with this many players in the pot, so it's not a bad move to raise it.
That said, EVEN in this pot, if you put out a couple of random hands against your AKKQds you'll find you're only a percent or two of equity ahead of the average, in most cases. Increase the number of hands and you (presumably) increase the number of midrange garbage cards, and you may increase your "lead" over the average 8-handed equity by a few more %. If you have something like a 15-20% equity in an 8-handed pot like this, then it's got to be a good move.
Like most rules, it's not a hard and fast rule but it's simply the case in O8 that it's almost never correct to raise a high-only hand preflop. The only exceptions would be when you have some chance of stealing the blinds, when you are advertising or trying to set someone up for some sort of macrogame play or when there's a ton of limpers and you hold something seriously nutty on the high side, like AAQTds or something. You USUALLY need a lot of other midrange hands in the pot for your nutty high end features to be worth a raise, which means a lot of loose limpers.
SO, as I said I can see a good argument for a raise here and as I also said I think it's a decent play. I might have done the same there.
Just making the point that, as a rule, high only hands in O8 limit are weaker than you might think, although the good ones are almost always playable (even calling a couple of bets cold) and in very, VERY rare circumstances a raise can be decent preflop.
You should note that high only hands should only be raised for this reason in late position; it would be horrible to push one in MP, get two calls from the EP players with decent hands and lose two players in LP who had ragged A3 and A4 hands - these wouldn't threaten your high and would've put two more bets in between them to chase the other end of the pot with you only making half the preflop investment to build the same pot.
But you knew all that anyways
suffice to say, I don't believe there's any "secret" to why many decent players say never to raise high hands; like most rules in poker, or life, there ARE exceptions, but they're so few that usually it makes a good rule of thumb not to raise these holdings. The only time I do is when I'm stealing blinds; even in the hand you described I would PROBABLY have just called preflop, but I would concede there is a very good argument to raise.
Monk
xxxxx