Hi Peter,
Thank you for your concern regarding on this matter. The main reason why we didn't allow some HTML code to be rendered in language string is because the translator was made by the public community at the Transifex and there are some cases before where some translation made by them are causing the entire page to be broken due to the improper format of the HTML in the translation.
There are also some languages in the world that using utf8mb4 character string such as Chinese character and Arabic that sometimes can messed up the HTML on the page. Hence a proper sanitizing is required to ensure those languages can be load correctly on the site.
If you would like to remove the sanitize process, you can go to your components/com_easysocial/themes/wireframe/helpers/miniheader/clusters.php and change the following code at line 25:
<a href="<?php echo $permalink;?>" class="es-cluster-header__title-link"><?php echo $this->html('string.escape', $title);?></a>
change it to
<a href="<?php echo $permalink;?>" class="es-cluster-header__title-link"><?php echo $title;?></a>
Additionally, you can use template override method to ensure the file will not get overwritten during update,
https://stackideas.com/docs/easysocial/administrators/templating/template-overrides .
Hope these can clarify the issue here.