I want to know whether there might be an expression along the lines of "Convey X". Meaning, to serve as testament of X's character. I suspect that convey is not the correct verb, but I wonder if a suitable one exists.
This question will be difficult to answer because you are requiring a verb with
- a specific meaning, and
- a specific argument frame
By a specific argument frame, I mean that you want a transitive verb whose subject refers to some past action or event, and whose object refers to the person for whose character the past action or event speaks.
If we drop the second requirement, there should be a few candidate expressions. To give a couple examples with metaphorical uses of verbs of speaking:
Thomas' refusal to sign for the package was telling.
It says a lot that Thomas came to work on time even after what happened.
Both of these types of expressions would have the meaning you are looking for.