On s'est demandé v. on s'est sentis - l'accord du passé

Question

In the first example, "se demander" does not agree in number or gender because the reflexive pronoun "se" is an indirect object.  Why doesn't that same rule apply to "se sentir" (I feel)?  Thanks.

Accepted Answer

Hi Sean, 
The rules of agreement of past participles in the case of reflexive verbs are highly complex and as you rightly point out can depend on whether the reflexive pronoun acts as an indirect or direct object pronoun. Some reflexive pronouns cannot be analyzed in such a way and in this case, the past participles agree with the subject -

Je me suis évanouie quand j'ai appris la nouvelle = I fainted when I learnt the news
Ils se sont tus, soudainement = They shut up all of a sudden

I think 'se sentir' comes under this category. so an agreement is required.
On s'est sentis mieux = We felt better
And of course, there are exceptions to the rule like the verbs, se plaire, se rire, se déplaire, se complaire which don't agree at all.
Elle s'est plu à ignorer sa présence = She enjoyed ignoring his presence 
These are rules that even French people get wrong because even if they know them, a lot of analysis is required.
I hope this sheds some light on the intricacies of reflexive verbs.