In my view, the phrasing T t = E; simply determines how the conversion works and which conversion functions etc. are invoked. Once that is done, we have a converted expression f(E) (here called t) that needs to be a constant expression. You seem to be concerned that, for the prvalue case, the actual initialization isn't covered by the "constant expression" constraints. I don't think so, because in the cases where we yield a prvalue, we actually have a (symbolic) initialization of that prvalue in view. E.g. a called function would use copy-initialization in the "return" statement, which imposes the appropriate constraints, even if the prvalue model does not supply an actual target object until later / outside.

Presumably, the intent should be that meaning. However, when we say "X" (shall)is a constant expression, we just concern about whether "X" itself satisfies the requirements to be a constant expression. Such as

static int value = random();  //#1
constexpr int& rf = value;  // #2

As per [dcl.constexpr] p10

In any constexpr variable declaration, the full-expression of the initialization shall be a constant expression ([expr.const]).

In this example, we require the full-expression of the initialization at #2 should be a constant expression, especially, we only concern whether lvalue value is a constant expression that is a glvalue core constant expression. At this declaration, evaluate value won't violate any restriction in [expr.const] p5, which also says we don't need to concern about how the value is initialized. Analogy, when we say "converted expression" is a constant expression, we only concern whether that "converted expression" itselft satisfy the requirement to be a constant expression, since there is no result object in such as "template-argument-list", "explicit(constant-expression)", "noexcept(constant-expression)", "[constant-expression]", evaluate such a prvalue seems not to have an effect(i.e. recover the scene of the process of the initialization). This is my concern in this issue.

As you said, we should consider the process of the initialization in this context, however, if we use the way of interpreting "X shall(is) a constant expression" to interpret "converted expression", as aforementioned, it seems a bit contradict, and "converted expression is a constant expression" actually may not expound the intent that we should check the emulated initialization imposing on that prvalue("converted expression").

In other words, we need to inspect what will happen(evaluate) in the whole implicit conversion that converts the source language construct to the expected target one, the "converted expression" is just the result after performing that sequence of these evaluations, we cannot recall the whole process just through the result, it is a bit philosophical utterance but is true.

Maybe, change it to that will be more clear

the implicit conversion sequence is a constant expression when interpreted as a constant-expression.

Then evaluate this constant-expression will be equivalent to performing the corresponding declaration and initialization.

I suppose you shouldn't think in the way that "considers a variable definition an expression". It's obvious that T t = E; is only used for determination of well-formedness and which conversions are used.

IMO conversions and object/reference initializations need different "interpretations" when determining whether they are constant. And it is more consistent for me to include "expression s (grammar productions) plus needed implicit conversions to target types" into expressions.

T t = E; is a convenient way to expound that conversion and examine whether the conversion is well-formed. [conv#general-6] explicitly says that

The effect of any implicit conversion is the same as performing the corresponding declaration and initialization and then using the temporary variable as the result of the conversion.

They're arguably equivalent.

it is more consistent for me to include "expression s (grammar productions) plus needed implicit conversions to target types" into expressions.

Isn't that what contents I claimed to improve in this issue? I prefer to interpret the implicit conversion as a constant-expression, and evaluate this constant-expression can view what stuff the implicit conversion needs to evaluate. Since we have used a similar utterance to expound "full-expression of the initialization". According to [conv#general-6], the evaluation of this constant-expression would equal to perform the initialization in the declaration

T t = E;

This proposal may make these rules consistent.

IMO it's better to specify expressions, constant expressions, and implicit conversions in such way that no additional "interpret" is needed.
Given that a conversion can have its type and value category, while a variable definition shouldn't have, I think a formal definition of "expression" that includes implicit conversions (and thus more general than expression) should be present in [expr.pre].

It is impossible to specify conversion to be an expression without "interpret" as if it is an expression of grammar. Moreover, regardless of the category value or type of the conversion, they're all specified in [conv#general-6]. Redefine them is redundant. We just lack the relevant phrase about the evaluation of the whole process of the conversion, even though, the whole conversion occurs in that context.