Hi Tim. 
I run into that problem yesterday - I posted a comment with a picture in it, nothing to fancy and heavy, but apparently the network was heavily loaded so It was enough to stop me from doing anything at all in the platform.
Luckily I had some SP waiting so I waited to have some more bandwidth and redeemed it and I got back to acceptable Amount of bandwidth. I have 122 SP and I power up everything I have and yet it happened.

I do think the bandwidth restriction is necessary as there are a lot of spammers trying to earn some upvote with their spammy comments, but - it should be a little higher as it restricts honest users like me when we are commenting or posting photos etc.
I defiantly like that having more SP expands the bandwidth as it will make people invest in the platform instead of cashing out and milking the platform. I power up regularly because I believe in the platform for the long term.

Users with huge bandwidth and SP probably dont need such high amounts - maybe we should limit the upper threshold and spread the reserve to the rest of the users?

And two questions if I may @timcliff:
1. What is the current rate the bandwidth restores if there are no changes to the network's load? You say a week, so it's 100/(7 days * 24 hours* 60 minutes)?
2. May I translate this post to Hebrew and publish it? It's immensely helpful.

Thanks, Nati.