I've had a look at the patch and picked up the following:
line: 34 - $navcount not needed, that's a navigation block static used to count the number of nav trees on the page
line: 49 - Is the global CFG needed?
line: 82 - copy and paste Guessing that should be true as well.
line: 92 - PHP docs required
line: 96 - I don't think the block should override that at all, it should just use the default function
line: 117 - Again not needed
line: 119~135 - That code shouldn't be in the navigation block, let alone this block, I'll create an issue to clean it up from the navigation block.
In general it would pay to search the code for the word navigation and then look at fixing the comment/docs/uses if need be
The only other thing I noticed is that both the navigation and admin tree are being used to locate the things, the admin tree is being used to locate bookmarks, and the navigation is being used to locate the page the user is on.
Having looked at the code I don't think one is better than the other for this task, but I do wonder whether we should use one and not both.
Either way perhaps not worth worrying about right now, certainly not as part of this issue.