MacBoo wrote:
Labhrás wrote:
No lenition of past tense autonomous (dúnadh), but h prefixed before vowels following níor, nár, sular, etc.
Yeah the autonomous mostly resists lenition, but I don't remember ever hearing
nár, etc. causing
h prefix. Or is it only with the autonomous?
I used the autonomous because the concept of a door closing or opening without the help of an agent doesn't sound right to me, but that's just me being pedantic, I suppose....

Yes, h-prefix only with autonomous form in many dialects - but not in Standard Irish, so nár osclaíodh is correct.
Many verbs have transitive and intransitive meanings (somebody opens the door, the door opens). The autonomous form implies an agent and is active. And both isn't meant here. I can only compare with French "on" or German "man": "Wenn man eine Tür schließt, öffnet man eine andere" doesn't make much sense because it is not the same person who closes a door and opens another.