・・・言いたいことは色々あるのだが、ここで口を挟むのは野暮というもの。の英語

There are things I'd like to say but to butt in now would be what they call uncouth.

I don't want to be a killjoy, but I'm a little skeptical about that.

I must clear myself of the false charge.

Between ourselves, he is not to be relied upon.

It is for me to dictate to you, but won't a hundred yen do?

Between ourselves, he is not to be relied upon.

to speak words unclearly as if one's words are stuck in one's mouth

He is not to be depended upon, for he will speak on impulse―speak on the spur of the moment.

I have a personality in which I cannot settle down until I say everything that I want to.

Such remarks are sure to give offence―offend some one.

I will not waste words on a fool.

It is not for me to dictate to you, but won't ten yen do?

It's hard to say this without sounding like I'm disagreeing with you, but let me be upfront about it.

He knows what is what, though what he says sometimes seems unfocus(s)ed.

In other words, it takes all sorts of people to make a world.

Complimenting is lying.

He admitted the fact with an embarrassed air―with a bashful air.

I don't care about sounding natural. I just want to be understood.

I know this sounds like interference [as if I'm interfering], but can I suggest (that) you don't get involved?

A casual remark can hurt someone.

I know it seems like I nag, but your attitude is bad.

It defies description [criticism].

I find just the memory of his overly polite patronizing manner really offensive.

He is not to be relied upon, for he will speak on impulse―speak on the spur of the moment.

I must put you on your honor not to speak of this to anyone.

It is proper that a man should scruple at―be scrupulous about―have scruples about―the slightest departure from the truth.

Even if it were so, that would be no excuse

Granting it to be so, that will be no excuse.

No matter what I tell him, it's useless, so I don't interfere anymore.

to hesitate to say something because it is secret