Hoje, isso depende de como você copia.
Usando o botão de copiar:
insere apenas a versão de texto na área de transferência, entre outros:
TIMESTAMP,TARGETS,SAVE_TARGETS,MULTIPLE,UTF8_STRING,STRING,TEXT,text/plain,text/plain;charset=utf-8,chromium/x-internal-source-rfh-token,chromium/x-source-url
mas copiar o texto real funciona:
já que você está copiando o HTML renderizado pelo navegador, em vez de ter o Discourse interagindo com a área de transferência, o formato text/HTML fica disponível para consumidores da área de transferência:
<span class="hljs-meta" style="color: rgb(133, 133, 133); font-style: italic; font-family: "JetBrains Mono", Consolas, Monaco, monospace; font-size: 15.75px; font-variant-ligatures: none; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: pre; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">@@ -1,11 +1,11 @@</span><span style="color: rgb(199, 199, 199); font-family: "JetBrains Mono", Consolas, Monaco, monospace; font-size: 15.75px; font-style: normal; font-variant-ligatures: none; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: pre; background-color: rgba(0, 0, 0, 0.25); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">\n</span><span class="hljs-deletion" style="background: none 0% 0% / auto repeat scroll padding-box border-box rgb(79, 24, 11); color: rgb(222, 113, 118); font-family: "JetBrains Mono", Consolas, Monaco, monospace; font-size: 15.75px; font-style: normal; font-variant-ligatures: none; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: pre; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">-Young volunteer award – celebrating young volunteers, aged 16-24, who go the extra mile in their local communities, demonstrating our values and the importance of connection and action.</span><span style="color: rgb(199, 199, 199); font-family: "JetBrains Mono", Consolas, Monaco, monospace; font-size: 15.75px; font-style: normal; font-variant-ligatures: none; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: pre; background-color: rgba(0, 0, 0, 0.25); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">\n</span><span class="hljs-addition" style="background: none 0% 0% / auto repeat scroll padding-box border-box rgb(11, 66, 32); color: rgb(118, 196, 144); font-family: "JetBrains Mono", Consolas, Monaco, monospace; font-size: 15.75px; font-style: normal; font-variant-ligatures: none; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: pre; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">+The Young Volunteer Award celebrates young volunteers, aged 16–24, who go the extra mile in their local communities, demonstrating our values and the importance of connection and action.</span><span style="color: rgb(199, 199, 199); font-family: "JetBrains Mono", Consolas, Monaco, monospace; font-size: 15.75px; font-style: normal; font-variant-ligatures: none; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: pre; background-color: rgba(0, 0, 0, 0.25); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">\n</span><br class="Apple-interchange-newline">
Para dar suporte a isso por meio do botão de copiar, seria necessário adicionar a capacidade de pegar a versão colorizada renderizada (já que a colorização é feita por uma biblioteca) e enviá-la à área de transferência com o formato text/html. Provavelmente é possível (talvez até como um componente de tema), mas, enquanto isso, sempre há a opção de copiar selecionando o texto.