Per esempio, Harry si svegliò alle cinque... Harry si voltò di scatto They are reflexive because they have "si" svegliarsi, voltarsi they have the accent because they are in the past third person singular (he/she). Without the accent they are in the present tense the first person singular ex. Io mi sveglio, io mi alzo.

Without accents they are in 1st person present, but if there is an accent on the ending O, then it is 3rd person of passato remoto, used very much in the literature. Good example is the verb ANDARE. the passato remoto form is andò, ma this could not be the 1st person present, since it is irregular form vado. So the accent does metter:-)

No. The accent means they are in the 3rd person singular of the PASSATO REMOTO.