There's some excellent stuff on those lists - only a couple of omissions spring immediately to mind, those being Dr. Strangely Strange's debut "Kip of the Serenes" (similar to the ISB but more melodic and less rambling) and Shelagh McDonald's two albums (currently only available on the two-disc set "Let No Man Steal Your Thyme").
Like Sin Agog and Hunter, I'm not 100% sure where folk-rock ends and acid-folk begins, but if the likes of Davy Graham and Sand Bull qualify
- which, given their penchant for drug use and continent-hopping mysticism, I'dd argue that they do - I'd also add virtually everything they released prior to the 70s. The same applies to the US Kaleidoscope, even though not all of their material is strictly folk-based. Some of Roy Harper's early releases like "Stormcock" would probably also fit the bill. Then of course, there's modern stuff like Six Organs of Admittance and Espers...
I agree about the terminology not being very helpful, but in general alt. folk terms I'd also recommend Fresh Maggots, and more recently In Gowan Ring.
ps: there's some wonderful moments on Mike Heron's 'Smiling Men With Bad Reputations', and the first eponymous album by Heron (no connection) is excellent.