I would consider using this app on my desktop instead of Thunderbird primarily due to the improved search.
After giving it a spin for 180 seconds, the main nuisance for me is that I can't elect to "Always show images from this sender". I use that in other desktop clients to ensure the image blocking banner doesn't end up being subconsciously ignored by me, as it will then only show for new senders who I'm not familiar with and need to be more wary of.
Also, like all banners everywhere no matter how well designed, it's ugly. In fact to be honest... this is the main reason I want the option to get rid of it.
I can understand why you don't offer that in the web app if you're storing it server side for each customer's list of saved senders, but for a desktop app where it can be stored locally, I'd value it.
German internet didn't seem so bad to me, and I suspect it is because I am Australian. The parallels between Telstra and Telekom were uncanny.
In Germany eventually I ended up with 50mbit VDSL which was fine, but having to get Telekom out to connect a phone line in a new building was not fun. Lots of hoops had to be jumped through.
Coming back home to Sydney, stuck on 3mbit ADSL2+ (4km from exchange) was also not fun, but at least it was upgraded to HFC NBN a year later. We're making progress... but as in Germany, it all depends on where you live.
When the shills in question are lazy, it can be pretty straightforward to detect, yeah. This sort of thing was very high on my list of "problems that will need mitigating if this has any chance of working" with my Suitocracy project.
The more research one does on astroturfing and the like, the more depressing it gets. Dedicated desktop VMs running different browsers and OS's, directed through different proxies to get different IPs, etc. Where social media is involved, detailed online personas are set up for each one, with reasonable histories for using later down the track.
I think the best we can realistically do is to raise the cost of successful astroturfing/shilling to the point where it might not be economical to do, at least on a meaningful scale. As others have said, community involvement and skepticism play a huge role in that.