Mingled math and text in math mode

I frequently encounter the situation of wanting to, say, write a set where the set-membership condition involves some text. If I wanted to describe, say, the set of all even integers this way, then would it be better to write

\{x \in \mathbb Z : \text{$x$ is even}\}


or

\{x \in \mathbb Z : x\text{ is even}\}


? Of course there are obvious quibbles (maybe you like \mathbb{Z} rather than \mathbb Z; maybe you like some other delimiter than :, or some manual space around it), but I'm asking only which way is preferable for writing intermingled text and math in math mode—and, if possible, a reason why other than personal preference.

(I was convinced long ago to use the former by someone who argued that it's semantically more sensible, but I don't know if it's the best practice, or, if it is, whether there's any TeXnical reason for it.)

Note Do not use this method for your actual work or in your professional capacity. It is a mere jeu d'esprit. This is not recommended for actual maths, which is 99% layout (such as glyph shapes, spacings and proportions and so on, to convey meaning in a standardized way), but is meant only to illustrate that all unicode glyphs are just that, glyphs, and so are "text-able" (as far as that can take anyone). There is a (natural) tendency to consider the (996) mathematical alphanumeric symbols as just a text glyph with formatting applied (e.g. bold, italic), or originating from a different font file/style altogether (e.g., sans, fraktur, script), but, in Unicode, all these 𝐱𝑥𝒙𝓍𝔁𝔵𝕩𝖝𝗑𝘅𝘹𝙭𝚡 are completely different glyphs (in the same font), not just the same text x codepoint in fancy dress (from potentially a mixture of different fonts).

Just to celebrate end-of-year, without delimiters ...

If I type directly in unicode:

𝑥 ∈ ℤ : 𝑥 is even


(and the font has text Latin in it as well, like XITS Math does), then I get:

MWE

\documentclass[border=6pt]{standalone}
\usepackage{fontspec}
\setmainfont{XITS Math}
%\usepackage{unicode-math}
%\setmathfont{XITS Math}
\begin{document}
%$x \in \mathbb Z : \text{x is even}$

𝑥 ∈ ℤ : 𝑥 is even

\end{document}


... so the question is moot, perhaps. :)

• Sorry, but I don't recommend this way. The 𝑥, ∈ and ℤ are treated as in text mode, so unexpected things may happen. Moreover, the spacing is not the "standard" consistent math spacing, but only a normal text-mode space. – Fractal is at topanswers.xyz Dec 30 '19 at 10:59
• I agree with @Fractal, this is not the way to go, sorry but -1 – CarLaTeX Dec 30 '19 at 11:01
• @CarLaTeX I don't think a downvote is necessary. From his wording, it is quite clear that this answer is not meant to be serious. It is kind of "just for fun". – Fractal is at topanswers.xyz Dec 30 '19 at 11:03
• @Fractal I like fun posts but not if they give wrong information. – CarLaTeX Dec 30 '19 at 11:10
• @CarLaTeX Ah, I remember that sad episode. – Fractal is at topanswers.xyz Dec 30 '19 at 11:11