Like a kind of subscription model where you "subscribe" to scientific topics, for example, and then receive suggestions.

Yep, that's one of the first specializations that I had when I first started the project. I created the @thoth-stem account around the same time as @thoth.test for eventual use as a Thoth account that could focus just on STEM topics.

However, if they act in general terms (as I understand the current approach), a comment in German (or another language) would suffice for me to then read the article in its original language.

I agree. With current usage levels, I think that's the most useful service that Thoth is able to provide to readers right now. If I see a title in a language that I don't know, I have no idea whether I want to read the article or not. The single-language summary from Thoth helps me to make an informed decision about clicking through and translating the original post with almost no effort. It was an accidental feature, but it feels extremely useful to me.