There's absolutely no doubt in my mind that he abused his voice during shows during the latter half of the 80's and combined with heavy smoking it had a detrimental effect. His voice was at its weakest during 97-03, recovered some of its strength during the Bomb era and during 360 he learnt to make the best use of it like a driver being careful with an old clapped out Ferrari which he knows will never be in mint condition again. Compared to some of Bono's peers (Stipe, Gahan, Rose) his voice is nowhere near as good as it was in his heyday. IMO a singer's responsibility is to take the utmost care of their voice. Just as guitarists don't handle power tools for shits and giggles, so singers should stay away from heavy smoking. Bono clearly didn't and all the albums from Pop onwards have suffered for it.
I agree with all you say, except for the "Bono's peers" bit. Michael Stipe? Axl Rose? Dave Gahan? Stipe has a miniscule range and is not a great singer, IMO. His voice works for his songs - and that's true for a lot of bands. They write music that works with their lead singer. But comparing Bono and Stipe is not logical. Gahan has a very deep voice - good singer, but very limited range. Sing that deep and you'll never have to worry about not hitting a high note - there aren't any. Rose? I admit, I haven't heard any recent Rose, but Rose from the past was all about this weird screaming voice.
If you want to compare Bono to anyone, use Freddy Mercury or Jim Kerr. Both of those artists would belt out their tunes. Mercury was known for his fantastic range. I would contend that the Bono of '86-90 was like them.
Bono made a conscious decision NOT to sound like that come 1991, but I'm sure he could have belted that way for a few more years.
But the toll of smoking, over-singing, constant touring, not having proper vocal training, alcohol and even age hit him hard come the mid-90's. I was stunned at some events in '95 and '96 when Bono sounded like a fraction of the singer he was. In contrast, shortly before Mercury's death, while he might not have quite had the power in his voice - due to illness - he certainly had the range and sweetness of it. I think smoking was the main problem for Bono. One can smoke and sing, but one can't sing like Bono wants and smoke.
Something during the HTDAAB era, he regained that voice. Listening to him belt out "Miss Sarajevo" was mind-numbing - he sounded MORE powerful than he did during the best LoveTown days.
So no smoking, some vocal training and treating the vocal chords gave him his voice back. Yay! But why renew this thread then?
Even though Bono has it, fear of his past, IMO, has often held him back some now. I hear him singing a bit lazily at times now, something I never heard before. He hums the words, but doesn't always have the passion behind them. And a cautionary Bono - while technically still a solid singer - isn't quite the great singer of the past.
But I'd rather have him burst out one or two times a night during a special song, then twice in every song as he did in the past. That's partly what ruined his voice.
However, Bono will always be oceans above Stipe, Gahan and Rose.