In cases of very egregious spam, Google is willing to hand edit. For example, Google will hand edit to remove something like adult content showing up on a Disney search. So they don't always wait until they can close the hole in the algorithm. But hand editing is more used for removing a really bad URL from the SERP, and not for boosting a result.
I hear you - but that's still an edit to the algorithm and not a hand edit to an individual SERP.
Also, from what I see, it's more than multinationals that are considered brands - although I can appreciate that users would respond well to them in the SERPs. Even a niche player can build a "brand" that Google recognizes.
Are users doing navigational searches for your site? That's one sign of a brand. Google may also be using unlinked mentions and even offline references, possibly RSS feeds, email newsletter, and on and on. And IMO, anyone who is working for web traffic, even a niche player, should be working to build their brand.
Google absolutely hand edits Serps, in the form of penalties. This happened recently when they tested the new layout for local search. Several sites that had pages targeting local terms with relevant info were dinged. So when their 'quality testers' find something that doesn't align with an algo tweak (in this case showing companies with a physical location), they hand edit by applying penalties.
Even if your pages and content are relevant, informative, and non-spammy they will still edit the results to ensure their algo updates are working properly.
Hand editing results would be impossible , except in serious cases of spam abuse.
Certainly Google uses it's editing techniques alongside it algorithmic systems. Here's my speculation of the sequence :
SERP results and simply sites are flagged for review by editors if :
-traffic patterns and quantities seem unatural -if traffic doesn't match the theme of the site -difficult verticals receive a site with a sudden boost -link patterns and link quality seem unatural
+ adverse user data intelligence e.g. complaints , results not matching , time on site etc etc
Even if my speculation is off the mark, Google surely let's it's algorithmn take care of the systematic side before referring it to several tiers of editors , perhaps within a heirarchy of responsibility. The first level may just be ticking boxes on the site's internal profile. From what i understand , the guidelines for editors are tight , but i do worry about how their discretion might be applied.
Editorially , i think site wide intervention is more common , rather than individual result handling. So that tends to be dished out with penalties , like the minus 50.
The issue of the sites respectability , ie " trust " may play into this. Site's with "trust" seem to escape with a lot of discretion. I think trust is measured by brand and the quality of inbound links.
If you're a nobody and you start to rise enormously with traffic , expect a knock on the door to review your site's condition. Google is going to ask how is this site contributing to good SERP's - but i stress this is for large traffic sites coming out of the blue. Small sites with small traffic may be just subject to the rigours of the algorthimn with no ceditorial considerations.
But clearly , unless Google tell us how they operate their guidelines infinitum , I don't know for sure ... it's just my hunch based on experience and a crystal ball.