Learn Russian: Нам не стоит сожалеть об этом вложении.

Both translate to "we shouldn't", but they have different nuances. Нам не следует is a direct recommendation meaning "we ought not". Нам не стоит literally means "it is not worth it to us". It softens the advice, implying that regretting the investment is pointless or won't bring any benefit.

Why is "we" translated to the dative pronoun нам instead of the nominative мы?

Because стоит in this context is an impersonal verb. In Russian impersonal constructions, the logical subject—the person receiving the advice or feeling the state—must be in the dative case. The sentence literally translates to "To us, it is not worth regretting..."

Why do we use the imperfective verb сожалеть here?

When giving negative advice or stating that an action is unnecessary (using phrases like не стоит, не надо, or не следует), Russian strongly prefers the imperfective infinitive. It conveys the general idea of "don't do this at all."

What case is этом вложении, and why does the noun end in -ии?