The only possibly shady thing you point out is that it's opt out, I get that. Especially people who want to block everything unconditionally might feel cheated because it's not called Adblock Minus.
What Mozilla did here, OTOH, I find shady because they're pretending to run an impartial addon store, when in practice some guy who wants to promote a specific extension (maybe that person feels like you, maybe he's a friend of gorhill - I have no way of knowing) can pull these kind of tricks.
But I suppose it's a case for Hanlon's Razor: They probably just don't have their stuff together about running any type of store the way the big guys do.
I'm still a proud Mozillian, I can find one thing they do shady without finding all of Mozilla shady, I realise it didn't sound like that above.
P.S: Ublock Origin is not just an adblocker. It can block various types of content.
AdBlock Plus seems to whitelist your ads if you pay them millions [1][2]. The euphemism ABP (and their parent company Eyeo) uses is 'acceptable ads'. Acceptable to Eyeo I guess. It's opt-out at the users end.
OP knows all about this [3][4].
I'm not a fan of some of Mozilla's policies but I'm thankful if it's true that Ublock Origin is shown preference over the shady, user-disrespecting ABP.
[1] Google paid AdBlock Plus to get its ads whitelisted https://news.ycombinator.com/item?id=5995140
[2] gorhill, UbO developer on Eyeo https://nitter.net/gorhill/search?f=tweets&q=%22eyeo%22
[3] https://news.ycombinator.com/item?id=6818307
[4] https://news.ycombinator.com/item?id=5946892
[5] Eyeo on HN https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...
[6] https://news.ycombinator.com/item?id=28746231