Should I consent to exec to give feedback about HR to the CEO if my evidence is ...

In a previous post, I explained how HR questioned me for spending informal time with interns. During that conversation, HR warned that this could be viewed as "hitting on them" and might start rumors. I reassured them this wasn't the case. In that very same meeting, they actually praised me for taking a successful, informal approach to onboarding one of those interns, after having criticized me about that with my manager.

After this:

• I found out that HR repeatedly interrogated that intern about me. They asked the intern if they were "into me," if they were happy with their partner, and if they thought I was "objectively attractive." The intern dismissed the comments.

• an executive found out about these comments at the point above (along with other toxic HR behaviors). They believe HR is damaging our startup's culture and want to give explicit feedback to this same HR person and to the CEO

• that exec is now asking for my consent to mention my gripes. Furthermore, they want me to discuss this with my direct manager (another exec) before they proceed.

While I fully agree with the exec and I am actually avoiding the intern as much as possible because I fear HR is unfairly evaluating me, I am hesitant to get involved for two reasons:

1. HR never accused me of hitting on interns directly. In fact, they praised me when I confronted them face to face. My grievance is entirely based on what the intern later told to me. I fear I don't have enough solid ground, and taking action might do me more harm than good

2. I am very reluctant to bother my manager with drama that as of point 1, I don't feel stands on solid ground, at least on my end

So, should I allow this exec to include my viewpoint in their feedback to this HR person and? If so, how do I navigate the fact that my side of the story is based on second hand information (and somewhat contradicts the praise HR gave me directly)?

They believe HR is damaging our startup's culture and want to give explicit feedback to this same HR person and to the CEO

That seems like a good thing to do: that HR person feels way out of line and your best path is to support this activity especially since it has full executive approval.

I fear I don't have enough solid ground, and taking action might do me more harm than good

You have what you have. Just be truthful and as accurate as you can be and leave the rest to the executive. Hearsay is fine, if you mark it as such. You weren't present when HR talked to the intern, but you DID have a conversation with the intern about.

I would suggest to simply write it down with as much detail as you can remember. Something like this.

May 15: 10:12am: Meeting with HR questioning my break times and intern interactions
May 20: CTO mention HR concern during review meeting
May 23: Had conversation with intern at which told me that they haven repeatedly question by HR about me hitting on them, which the intern dismissed
...

You clearly mark hearsay as such, and writing it down makes everyone's life easier because they work of the same set of information. Just make sure everything is accurate, focuses on facts (not emotions), don't blame or complain, just describe what actually has happened.