As someone who works a lot with panels in cinemas, which frequently have to stay live during my work, I can understand the concerns. I've always preferred to work any panel dead, regardless of age, location, or even if I'm familiar with it by past experience. In my setting, there's usually a breaker or fused disconnect that can be opened and locked out. I do so whenever possible. If not, I ensure that I wear as a minimum gloves, long-sleeved cotton shirt, safety glasses and stand on a rubber mat. I also NEVER stand directly in front of any disconnect, breaker or fuseholder when operating same. I also look away during any switching or resetting operations. So far, I've only had damage to one pair of gloves when a 100amp 240v breaker exploded.
But in residential, many panels do not have main breakers or disconnects. So what's left? Pulling the meter? Not a good idea. I've had one explosion there too, when I worked for a local EC. The socket supports had broken down and failed as I pulled the meter. I was extremely lucky as I wasn't wearing the proper PPE that time. O.K., that leaves disconnecting the service drop. Not only do most POCO's frown upon anyone messing with the drop, that's a lot more dangerous than pulling a meter or removing a cover.
Working with that EC made me familiar with a wide range of panel brands, and I quickly learned the clearances to live parts in each brand. Some residential panels have less than 1/4" clearance to the load lugs when removing/replacing the deadfront. Others have adequate clearance, but if not careful it was possible to miss the mounting stops and contact live parts.
I apologise to everyone for the length of this post, but the topic raises a lot of questions. My humble advice to all would be:
Familiarize yourself with as many types and brands of panels, switchgear, etc. If possible, study the construction with the power off and try to visualize any failure modes or clearance issues.
Invest in and wear the proper protective gear if panel removal is one of your duties. At the minimum for residential, gloves, safety glasses and non-synthetic clothing with long sleeves. Anything over 240v or commercial of ANY voltage, add a flash jacket!
If power-down is not an option, NEVER WORK ALONE!(I refuse to do any live work without an observer.) Have someone who can at least call for help if needed standing by AT A SAFE DISTANCE! And they MUST NOT be looking directly at the equipment at any time, an arc or flashover can cause eye damage even at a distance.
The age and external appearance of the equipment involved can give you an idea of how safe/not safe removing panels can be. Of course, some brand-new gear can fail or be dangerous too. But if it looks well maintained, there's a fair chance that it's a lot safer to work on that something that looks hacked/corroded/beaten.
Thanks for letting me throw in my 2cents here.