This has been reported several times:

• https://itch.io/t/2432416/the-reviewing-is-broken
• https://itch.io/t/1271931/cannot-paste-in-a-review
• https://www.reddit.com/r/itchio/comments/o0egg1/is_anyone_else_unable_to_pasteuse_the_clipboard/

As of november 2023, I found a workaround: type this in your browser console:
window.$.Redactor.prototype.paste = () => ({})

I do not fully understand the underlying problem, but I found out that itch.io uses the Redactor rich text editor, and this line of code disables all the convoluted clipboard-pasting management that this Javascript library does.

You can configure your browser to run this JS code line on every visit on a itch.io game page by using a GreaseMonkey or ViolentMonkey script like this:

// ==UserScript==
// @name        itch.io-clipboard-paste-fix
// @namespace   Violentmonkey Scripts
// @match       https://*.itch.io/*
// @grant       none
// @version     1.0
// @author      Lucas Cimon
// @description Enable clipboard pasting in itch.io review forms
// ==/UserScript==

window.$.Redactor.prototype.paste = () => ({})

Sombre est un jeu de rôle d’horreur. Il met en scène des antihéros qui essaient de survivre dans un monde particulièrement violent et hostile. L’univers de jeu proposé est celui des films d’horreur.

C'est une création de Johan Scipion dont j'affectionne particulièrement la version Sombre Zéro, car …

This is your room and you are in it. Face and shoot a variety of visitors. Then you can finally be alone in your room!

Boss-battle FPS in a very tiny square space.
Nicely done and fun!

HARVEST RESOURCES
IMPOSE YOUR WILL
DISCOVER THE UNKNOWN

This game takes about 10-15 minutes to complete and ends with a "thank you for playing" screen.

A short, funny and surprising clicker game by the excellent Daniel Mullins, made for Ludum Dare 52

Top down puzzle game about manipulating the tracks to redirect the trolley to save the victims. Solve the trolley problem in various forms of tiny puzzles.

Play the role of a muscular priest exorcist in his 50's. You are on a hike across the country, walking from town to town, banishing demons from houses. A boring classic routine.You just want to finish the job as fast as possible to get the money and find a new client.

A fast FPS with a "cleanup" routine, in a gripping and riveting world, as usual with Antoine Fauville.

AAAAXY is a nonlinear 2D puzzle platformer taking place in impossible spaces.

Sheep may safely graze is a relaxing game about building enclosures for sheep, based on a given amount of stakes and sheep positions. You will also have to handle black sheep, that must not be included inside the enclosure!

Un puzzle game court et mignon pour se faire quelques nœuds au cerveau en comptant les moutons 🐑 😄