For the average person, how much weekly fat loss is reasonable/safe while maintaining one’s muscle mass? I ask that because I want to shed some fat off of my frame but I don’t want to go into so much of a deficit that I sacrifice some of my muscle mass. I’ve heard some say one pound, others say two. Also, would a low/moderate carb diet be best?

As ever, there is the party-line answer and the real-world, trenches answer.  I'll give both.

Standard-issue fitness lore will tell you that you can (and, implicitly, should) shoot for losing a pound of fat a week.  The average clipboard-jockey in the too-tight, brightly-colored polo at your local Pump-It-Torium will tell you that if you want to lose fat, you should cut out 500 calories a day and over the course of a week you'll accumulate a caloric deficit of exactly 3500 calories, which is, conveniently, the number of calories in a pound of fat.   

Pumpy will also likely tell you that 500 calories equals a Snickers bar and a beer, a bag of peanuts and two cans of Mountain Dew, or seven cashew nuts, forty-seven Peanut M&Ms, and four Cheezy Fish, and so losing a pound of fat a week is actually EASY and EFFORTLESS and you won't even NOTICE the calories you've cut!  Then he'll whip out his desk calculator and tell you that on this system, you'll lose 52 pounds of fat in one short, painless, hunger-pang-free year!  How's that?   

Then you'll drool, nod, and hand over the cash for a huge block of personal training sessions with this joker.  

scale

I'm starting to think it's a bunch of hooey. 

For one thing, seven goes into 3500 just a liiiiittle too neatly for my taste.  I can't say for sure that the 500-cal-daily deficit thing doesn't work; the theory sounds okay, but in practice--in this trainer's experience--it's bound for failure.  

The selling point of this system is that you won't miss the calories you cut, but in reality, you do.  If you're not traicking it to a "T," you'll cut 500 calories one day, then go over 800 the next.  Your body's sneakily efficient in this regard.  Monitor yourself the next time you skip a couple of meals and tell me you don't belly up to the gluttony trough at the next opportunity.

Moreover, this method is so close to DOING nothing that it too easily slides into BEING nothing.  That is, you figure, "Okay, I just won't eat the M&Ms I'd normally eat and I'll lose the weight."  No need to count calories, or exercise, or even do much of anything. 

So even if you start off well, pretty soon you DON'T monitor your calories closely enough to ensure the daily deficit, and you don't lose the weight. 

Broadening out a bit here, I think there's a threshold of time-commitment that any health-and-fitness goal requires below which you're overwhelmingly likely to blow it off.  There are, to use another example, exercise systems the demand just 4 minutes of exercise a day.  But they don't work--not only because, well, they don't work, but because if your program requires just four minutes a day, you won't do it. 

Counter-intuitively, I think a program has to require at least half an hour a day or you won't make time for it.  Same with dieting:  it's got to require a certain amount of baseline vigilance on your part, or your diet will last exactly until your next trip past the company bagel bar.

 I agree with Alwyn Cosgrove (probably because he's done the research and I haven't!) that the upper limit of weekly fat loss has probably not been conclusively proven.  As long as you're getting enough protein and exercising wisely (that's a big if, mind you), you're probably able to lose fat at a far, far greater rate.

In my experience with people who have lost significant amounts of weight, it's much more effective to attack the problem from all angles and GO FOR IT HARD 24/7 than to try to go slow-and-steady.  When it comes to negotiating with your fat cells, endless diplomacy is a much less effective strategy than an all-out blitzkrieg. 

Floury, starchy carbs are indeed your most expendable calories, so I like diets that limit those more than super low-fat diets or other systems that allow you to eat anything (if you can eat anything within a certain caloric limit per day, how likely are you to choose the broccolli over the sponge cake?). 

My preferences aside, though, it's been shown that almost all popular diets work as long as you adhere to them.  Crazy, isn't it?  All the long-winded methodology that the ghostwriters for diet gurus spell out so meticulously is trumped by the one ingredient that can't be manufactured and packaged and sold in health-food aisles:  self-discipline.