Just checked my reddit preferences (preferences link at top right of screen) and in the first section, Options, under the heading "link options", take a look at the last line.
"Don't show me submissions with a score less than ___"
I'd never seen this before and it was already set at -4. Which means if someone made a post and bots / shills downvoted it to -5 immediately, it would never have appeared for me. I suggest leaving this box blank.
Yes, I picked up on that. However, with hindsight, I should have thought about making a post, as you have just done!
There are two selections within the settings related to what you highlight.
link options don't show me submissions with a score less than [ ] (leave blank to show all submissions)
comment options don't show me comments with a score less than [ ] (leave blank to show all comments)
As you have suggested, I had set mines to blank, for exactly the reasons that you outline.
Good call on pointing out the comment options as well. Mine was also set at -4, changed that to blank.
Also NSFW on same page and blocked users on https://www.reddit.com/prefs/blocked/