Some infomation that could help you
It seems to be in the baseUrl variable affection in the ccomment config
On my 5.0.2 site
compojoom.ccomment = {
user: {"loggedin":false,"avatar":"","token":"bcdbdfcea3ae51ba359033f43c60f4fa"},
item: {"contentid":1650,"component":"com_content","count":2},
config: {"comments_per_page":0,"sort":0,"tree":2,"form_position":0,"voting":1,"copyright":0,"pagination_position":0,"avatars":0,"gravatar":0,"baseUrl":"http:\/\/www.expemag.com\/","captcha_pub_key":"6Ld8ZegSAAAAAGw4956cmGTXRsT2_KKKo0Bck7HD"}
};
In the 5.2.2 site
window.compojoom=compojoom=window.compojoom||{};compojoom.ccomment={user:{"loggedin":false,"avatar":""},item:{"contentid":1650,"component":"com_content","count":2},config:{"comments_per_page":0,"sort":0,"tree":2,"tree_depth":5,"form_position":0,"voting":1,"copyright":0,"pagination_position":0,"avatars":0,"gravatar":0,"baseUrl":"http:\/\/www.lexpemag.com\/en-france\/les-landes-a-velo-pliant-et-packraft.html","captcha_pub_key":"6Ld8ZegSAAAAAGw4956cmGTXRsT2_KKKo0Bck7HD"}};
The php code which generate it, is in com_comment/helpers/utils.php where there is getJSConfig method
In 5.0.2 the code is
'baseUrl' => Juri::root()
in 5.2.2 the code is
$uri = JUri::getInstance();
$jsconfig = array(
[...]
'baseUrl' => $uri->toString(array('scheme', 'user', 'pass', 'host', 'port', 'path'))