A bit long, but here are my thoughts on French and Spanish accents…
I like them if they are pronounced correctly. Anais vs Anaïs, for example, makes more sense than Ophélie in an English context. Spanish José also makes more sense to me than French Léo.
Why? Because the dots on the Ï or Ë in French names serve a different function than the French É does, which again serves a different purpose than the Spanish É.
The two dots on a vowel such as Ï tell the speaker that the two vowels are pronounced individually, so ah-nah-ees rather than ah-nyes. Or in the case of Raphaël, rah-fah-ell rather than ra-fel.
In Spanish, accents don’t change the pronunciation of the letter but rather show the speaker where the emphasis lies. Spanish words usually have their emphasis on the second-to-last syllable, such as in the word “im-por-TAN-cia” (ia is regarded as one sound), so if the emphasis is placed on a different syllable, an accent is used on the vowel in that syllable, such as in “co-mu-ni-ca-ción”, where the stress is placed on the last syllable.
Same goes for José, which is now jo-SE rather than JO-se.
Here, accents make sense to me, even in an English-speaking country, because the sound doesn’t change
The é in French tells the speaker that the pronunciation/sound of the E changes, and not to the AY sound as many English speakers seem to think. In French, a vowel doesn’t make two sounds unlike it is often the case in English.
In English, the A is often pronounced “ay” in words like “late”, the position of the mouth changes - in French you would need to add another vowel to get that sound.
This is why I’m against using French accents in names that are then not actually pronounced with the French É sound.
Edit. I’m not familiar with Irish sounds/letters, however, as Irish names aren’t intuitively pronounced anyway (unless you’re Irish, of course), it makes sense to keep the accents, Roisin doesn’t exist as a name in English, especially not one that would have a similar pronunciation to Irish Róisín. French is one of the languages that influenced English the most and so French names are familiar and pronounced very similar to the French versions - which is why I think adding an accent would then require the same pronunciation as in French.