In Schumann op 15.3 "Hasche-Mann" Peters edition there are sfp markings on the first beats on m1, m3 etc. There is no such marking on the second beat of m4 even though it is similar (B/F# - D - B - F#), and also not on the second beat of m8. Funny thing is, in the counterpart of m4 at the next part, ie the last measure but one, the second beat (ie at B/F#) is marked sf. Is this how it should be played? What is the distinction precisely between sfp and sf in this context?
In my (old) Oliver Ditson edition, there are sfp markings on beat one of measures 1, 3, 5, 9, 11, 17, 19. By analogy, one might expect a similar marking on measure 7, although there isn't one. All the measures I mention begin with a quarter note tied to a sixteenth-note and it is the quarter note that is accented, so, by analogy, I don't know why you would expect an accent on the second beat of measures 4 and 8 where the right hand continues through sixteenth-notes. Playing this Vivace as indicated with an accent on the second beat of the measures you mentioned would certainly upset the rhythmic pulse somewhat, wouldn't it?
In other words, I don't think it's the tonality (B minor chord without the third) that dictates the place of the accent but the texture of the writing on those measures I mentioned.
That said and comparing the Urtext (Henle) with an edited (Schirmer) edition of the Op 12 FantasiestÃ¼cke, the editor in the Schirmer (Harold Bauer) has taken the liberty to "correct" some of Schumann's rather obvious inconsistencies in dynamics that remain in the Urtext.
I would use the structure of the music and the initial markings of Schumann in your copy and then use your judgement for the remainder of the piece. Can you justify an sfp marking on the second beat of measure 4? As for the accent on beat two of the penultimate measure: I don't like it because it doesn't make contextual sense to me.
You have to use your own musical judgment, I guess, or consult other editions.