With blockchains, updates to the system are called hard forks because it causes a split, or a new fork of the blockchain to take place. I guess it would be similar to changing from one car to the next while you're headed down the freeway. You're still going forward, but now you're in a different car as you do it. Hopefully, it's a newer, nicer, better performing vehicle. :)

I'm afraid I don't know all the reasons, or even the real reason. The official reason for the change to resource credits (RCs), which is only one change that took place, but the one causing the most grief currently, was to better gauge the costs of transactions on the blockchain and more fairly distribute those costs among the user base.

Everything we do has a cost to it, and they've been basically subsidized up until now. My guess is, Steemit Inc. doesn't want to continue doing that without some kind of collateral, ie, the users' SP. I'm not so sure how that all is supposed to work, but apparently the system has been looking at the cost loads of doing different things and is settling on what those costs are.

SP doesn't recharge. It's the RCs that do. SP is STEEM you have powered up in your account. It's what you've used to determine your percentage of control over the rewards pool (through the upvote amounts you can give). You can either power up more and increase it, or you can power down and then do whatever you like with the STEEM.

RCs, however, are like Voting Power. Depending on how much you do with it, can take seconds, minutes, hours or days to recharge. It depends on how much of it you have (based on SP), and what the cost is of those things you're doing. Comments and posts cost the most, powering up and other like transactions cost the least. Upvotes are somewhere in between.

You could certainly say there are accounts that are currently collateral damage in this change. High SP hasn't been affected. I'm not sure if they've ever been affected by anything, other than to improve their lot. Or so it seems. Other than to complain on behalf of lower SP accounts, I haven't read anything from a high SP account where the situation has been hampered.

I don't really consider myself high SP—I'm a large minnow—but I feel like I'm in a good place based on where we are at now, and even if they were to remove the patch. My account as is replenishes fast enough at the normal rate. I'd say the same holds true for any account that holds 2,000 SP on up. Below that, it will depend on how much everyone does.