Yes, to say that you have changed your mind about something as if that carries any particular weight in favour of that something is "dangerous" to the recipients of your message, as it's an underhanded debating tactic designed to persuade them of something that has no actual persuasive arguments in its favour.
can you point to where in the comment OP indicates that his opinion carries 'danger' for the audience? the comment is literally "i used to think this was irredeemable as well, however my personal opinion has shifted, caveated by the fact that i still agree that there are tons of scams and a crash coming"
Sorry, I'm not quite sure what you're talking about. For one thing, nobody else has "literally" said that; your comment is the only one Algolia can find with those exact words.
For another, I can't quite see what's not to get; what is it you're not understanding? saalweachter pointed out that "[i]t's amazing to [them] how universal the 'I used to be a non-believer' line is in evangelism" (Further expounded upon in https://news.ycombinator.com/item?id=29948754 ); throwaway98700k simplified to "[i]t’s a dangerous attitude because it has a paternal edge to it"; you asked whether it is dangerous to say that you have changed your mind about something; and I tried to explain that yes, it is, and why. (You might notice that my reply, like your question, was couched in quite general terms: The danger of "conversion" claims in general, without reference to any particular "OP" in this thread.)
But, to explain it again: No, of course OP doesn't indicate that their own opinion carries danger for the audience. (Would you?) That is precisely the danger, that "OP" (assuming you mean poof131) didn't acknowledge that their "conversion" isn't an argument in favour of "conversion", while still mentioning it as if it had something to do with anything (which, as saalweachter explained, tends to carry convincing weight in people's minds even though it logically shouldn't). Sorry, I don't know how to explain it better. Except, perhaps -- did you think this discussion is about whether the "conversion" claim would be "dangerous" to OP himself? That's not it. The danger is that conversion claims tend to persuade people more than they should; the danger of people getting duped into believing things that aren't true just because someone successfully (maybe even unconsciously) uses a rhetorical tactic.
AFAIK, I never claimed OP themselves indicates that their opinion carries danger. That's precisley why I agreed with the posters who did it for them, and spelled it out to you in my GP. Is there anything else in that, that you still don't understand? Besides your misapprehension that I claimed "OP" had said that, I mean (or possibly that the danger mentioned would be to not to "OP" but to the audience)? Which I sincerely hope is (are) thoroughly dispelled by now.