>> IMHO the bottom line is probably that if you are planning on adding a lot of coffee grounds at any one time it is better composted first.
I agree, since you used the words "a lot".
>> maybe the benefit of the worms might outweigh the nutrient tie-up?
I agree with that. Also, Nitrogen deficit is only a problem when N is already the limiting nutrient.
I admit it is hard to get added soluble N to the roots faster than microbes can suck it up, but "twice-weekly, weakly" ought to do a fair job of balancing that out.
My guess is that MANY gardens have a serious OM lack, somewhat compacted soil, somewhat poor-draining soil, few worms, and/or low water-retention. They would all benefit from adding coffee grounds into the soil or in a thin mulch, or a thicker mulch with coarse matter added to keep it "open".
Probably most gardeners willing to add chemical fertilizer already have over-fertilized soil, and any temporary Nitrogen deficit would be a temporary advantage! And if improved drainage helped the excess N to leach away, that would be a huge help.
All this is just my opinion.
