I agree that it is dangerous to talk about one's own attainments. Bhikkus are forbidden to discuss that towards lay people even and for good reasons.
What I don't agree with, however is the argument that it should only be discussed privately with one's teacher and not online. Many people here come to a forum like this for the very reason they don't have acces to a teacher (in person) and for discussing one's personal experiences we even have a special sub-forum.
I think it is ok for people who don't have acces to teachers to describe their personal experiences, so they can get feedback and find out what happened. Just don't claim anything, just describe.
IMHO this forum was founded to be the teacher for those who don't have acces to one in any other way. We are lucky to have many experienced meditators here, some even bhikkus, who can help all the others (like me