How should I say "I don't have anything useful to say so I am quiet"?

I am having a discussion/conversation with a very close friend, and this conversation concerns me personally (you might even go as far as saying this is my best friend). At one point in our conversation he starts to "spam" (not literally, the messages have meaning and are well-formulated) me with many messages, but I really have nothing to say back (or anything useful to say back). I should clarify by saying that I completely understand what he is saying, and I somewhat agree with the things he said.

He then proceeds to send me another text saying: "Don't you have anything to comment?.."

How could I respond nicely with a proverb/saying of any kind that means "silence is sometimes better than speaking when one doesn't have anything useful to say"...

I know some sayings like "silence is gold" or "better to remain silent and be thought a fool than to speak and to remove all doubt", but they don't really work for me in this scenario.

I hope I was clear enough. Thanks

Solution 1:

You clearly state that you understand all that your friend has said, but the description of your level of agreement with the content of the messages is "somewhat" less clear. It's, therefore, not totally clear to me if your hesitation to respond comes, at least partially and/or subconciously, from your lack of total agreement with the messages.
Since you don’t fully agree with (the gist of) the messages you could respond hedgingly with:

I’ll just say that it looks like you’ve covered/touched all the bases and I have nothing more to add [at this time].

If you do agree with at least the important points mentioned by your friend, you could hedge a bit less with:

I think you’ve covered/touched all the bases quite nicely and there’s nothing more to add.”

"cover all the bases (American & Australian) also touch all the bases (American): to deal with every part of a situation or activity"

(from Cambridge Dictionary of American Idioms via ‘The Free Dictionary by Farlex’)

(Granted, these responses are perhaps too polite, 'cause they'd probably be interpreted more as you complementing him on his thorough coverage of the subject than as you revealing your lack of interest/knowledge in/of the subject, but if you don't mind going full polite, they might work)

For an expression that relates solely to your silence without giving your friend the pleasure of thinking that he has “covered all the bases” (quite nicely or not) with his flurry of messages, you could simply:
Take/plead the Fifth

I take the Fifth
I take/plead the Fifth (Amendment)(American humorous): something that you say in order to tell someone you are not going to answer a question
Usage notes: The Fifth Amendment is the part of American law that says someone does not have to answer questions about themselves in a law court.

(again, from Cambridge Dictionary of American Idioms via ‘The Free Dictionary by Farlex’)

I’ll take/plead the Fifth [on that] on the grounds that anything I say may jeopardize our friendship!

Solution 2:

Couldn't you just reply with what you just explained to us?

'I understand what you are saying, but I'm not sure what you expect me to say.'

'I see what you mean, but I don't know what to tell you.'

'I see where you are coming from, but I think you should talk to [whoever is more concerned with the problem.].'

'I get your frustration, but I'm not sure how to help you on this one. (Good luck).'

Solution 3:

I don't have anything to add.

and/or

You've said it all.

Those statements indicate what I believe you're trying to say: that your silence is because of a genuine lack of anything to add and not indicative of disagreement.

Most quips on silence are intended to convey disagreement or lack of input out of personal ignorance. That's why you're having trouble finding one to match your intention: because for your intention going after "silence" quotes is kinda barking up the wrong tree. That's not what they are usually intended to say.

But just for fun I'll include my favorite one anyway, from Frank Herbert: "Silence is often the best thing to say."

Solution 4:

When I encounter this situation in conversation I reply "I'm just listening to/[or thinking about] what you're saying." It's neither a negative response nor a supportive response but I don't believe that I have to say something supportive in response to something I don't think merits it, regardless of how important the person is to me. I've never been pressed for further explanation but if I were, I would reply diplomatically about what they had said, not what I thought about it.