First things first. I never belay from my rope loop, and as a consequence I’m always told off by new climbers who have been taught how to climb the ‘proper way’ by qualified instructors. I’ve got no qualifications and I’m always told that I’m doing it wrong, and that I’d be screwed if I ever had to rescue anyone - to which I reply “have you ever rescued anyone for real?”. The answer is always a ‘No” and my reply is “Well I have, and I was using my belay loop every time”.
Here’s a few reasons why I don’t clip my belay device into my tie in rope loop.
Number one for me is that on a big route, the type of route you will most likely need to employ some rescue skills, I’ve seen too many belay devices get dropped when people untied (swapping ends, at bivys etc), forgetting their device was on the rope. Being on a huge wall without a belay device is far more hazardous than clipping your belay device into your belay loop.
Number two is that I’d like to see some test data (good one for you DMM) on cross loading of the rope loop (or triple loading, as you would on a hanging belay), both on the figure of eight and bowline (a cross-loaded bowline without a double fishermans knot to finish is death on a stick). The typical load on such a loop would be about 4kn, but could be up to 12kn - and well, although I place a lot of faith in gear, I’m aways a bit paranoid when it comes to cross loading (have a look at this video). It’s funny that we all know that even bodyweight can cause a cross loaded figure of eight on an abseil to fail (rather than the overhand used in the EDK), and yet we are happy to do just the same with one of the most important parts of the safety chain. I would bet that the number of hard falls onto rope loops is actually quite small as most climbers I know who take and hold a lot of fall don’t belay from their rope loop either. I’m happy to be proved wrong on this.
Thirdly - I don’t like being told what to do, especially when I’m being told to belay off my rope loop at Stanage. Like all climbing dogma I think knowing this technique and knowing when to employ it is enough (maybe with a very weak partner on a big route), but more importantly it’s vital to know how to escape when belaying off your belay loop anyway (prusik loop, taking the harness off, shear brute strength).
While we’re on the subject of belay loops, which by the way are probably the strongest part of your safety chain, some people seem to treat them as if they are only for belaying, and to do anything else would be dangerous. Well I for one have tied into my belay loop many times, as well as clipped my ropes into then with two krabs (when my life’s on the line I never trust a single krab in such a high load situation).
The reason for tying in to my belay loop has been when I’ve had to tie-in in the dark, or when the shits hitting the fan, and I just want to make tying in as safe and quick as possible. Trying to feed a rope through a harness when dressed in loads of clothes and gear can be tough (add mitts and it’s impossible), or when your hands are so cold and numb you can’t even tell if they’re even there anymore. A belay loop is a big secure target that is easy to grab and identify, and yes you can tie directly into it (even if the manual says not too).
If you want to tick all the boxes, and have a rock solid system, then you should always belay up your second(s) direct to the belay (guide style plate or munter hitch), so if there’s a problem you’re isolated from it. If you’re belaying the leader always make sure you have two prusik loops (1x 1.5m and 1x 2.5m of 5mm or 2x 1.5m of 5mm) and know how to tie off your device and escape the system in a real world situation (don’t practise on the perfect ‘instructor crag’ but in the dark, in crap weather, on route chosen at random).
Very often, in the real world, if the leader is in trouble the second can do very little, as most belays are not set up for an upward force (yes we’re meant to build them that way in books, but who really does?). The belayer is generally a weighted anchor, and so tying off the leader is not so easy as it sounds (the belayer will not have any extra protection either).
The answer in such situations is not to get onto such a situation, and if you do, belay loop or rope loop, you’d better hope the leader sorts it out!