ice climbing anchors and safety of follower/team

this is a really interesting conversation, thanks so much everyone for your thoughts. i'm really enjoying following along   

While getting in the weeds can be a fun way to waste time at work, The main takeaway here is that there is no inherent sketchiness of ice screws.   Assuming I caught all air, I’d whip the same on a bomber screw as on a bomber cam.  

But, like rock pro, The “art” is in knowing what’s bomber and what’s marginal.  For a screw, a “feel” for how it goes in — and what comes out the tube— can be one of the indicators.  And like rock, if it’s marginal, you want to place another better one as soon as possible.  

The odds are so much higher that something else gets you way before you blow out a two screw anchor, that it should barely crack your top ten worries on any ice climb, if at all.   

That said, to maximize your margins, consider vertically oriented fixed point belays with no extension similar to the pic below, vs horizontal screw placements with an equalizing feature like a quad.

There was an accident @ Lake willoughby about a decade or so ago where the leader zippered a whole pitch of about 6 screws. all with screamers. left tablet gets a lot of sun.  talked to a guy just last week who got an open tib fib from falling with crampons. people do it but it aint recommended. 

One of the easy ways to evaluate a screw as you are placing it is to observe the ice chips falling out as you screw it in. If they stop falling out for a couple inches, that means you hit a big air pocket / have drilled all the way through a curtain.

A real ice screw in good ice is often valued equally as a bolt in good rock. Unless you start placeing screws in shitty ice, it is pretty much a non-issue.

Yes - but if you're really climbing a lot of ice, you'll find some of your screws aren't as good as you hoped they'd be when you started them. Especially in Colorado.

Do you mean when they melt out?

Or when the ice turns out to have lots of big air pockets. Or any other time you decide you'd rather have a screw in less than perfect ice than no screw at all. Ice isn't always perfect.

Edit: it could be kinda chandeliered, really "cracky", a little slushy on the surface due to lots of running groundwater, super thin). It could be perfect ice, but with a relatively small attachment to the rock.

That's the whole point. Ice is not always good. Being strong enough physically and mentally to climb past bad ice without needing to wank around trying to get a good screw in a bad place is a good tool to have in your quiver.