DevDocs corrections part 1

Started reviewing the developer docs, finding lots of things to correct. I'll do more later, but please review this batch first so I know what, if anything, needs to be fixed moving forward - I'm not entirely sure on the markdownish format used.
I don't understand what this sentence is saying, although I'm guessing it has something to do with [BIP30](https://github.com/bitcoin/bips/blob/master/bip-0030.mediawiki).  Could you please clarify?