It is incredible, how HN community (arguably made from some of the lest dumb people on Internet) can turn blind eye to this major concern while laughing and patting themselves on their backs.
I guess, industrial magnates of 1800s would have shown the same reaction, if someone told them about dangers of burning fossil fuels.
"This is ridiculous!", "But Sun was causing fires for centuries!" and "If it gets bad, we can stop burning more coal!" — those excuses didn't age well, yet most replies to this comment repeat them almost verbatim.
Of course, instantly sending all (or most) of Earth hydrogen into outer space is impossible — at the current technology level. But wasting what little water we have to make it is still a bad idea.
Many places are already short on fresh water — the kind of water, necessary for electrolysis. We can make hydrogen from saltwater too — after purifying it, but that's not commercially viable. No one uses "free" energy from solar panels to make new lakes or refill depleting aquifers.
Most of the Earth's surface is covered by water, but we can't even purify enough to satisfy our biological needs — otherwise Sahara would be a major agricultural and economical attraction. To solve world's water problem would require near-unlimited power, and the hydrogen production is not going to do it. At best, a hydrogen boom would result in another round of colonial robbery: stealing water from people, who can't defend it, to power more air conditioners in USA and Europe.