Hello Javier
Harold opened up the question on behalf of me (as result from a ticket), that's why I'm answering.
Thanks for the answer, alas that does not work in Jira cloud.
Harold Oconitrillo Wouldn't it be great if your documentation providedan explicit statement that in Jira Cloud there is no way to change details of the proxy user let alone replacing it as it is possible on premise? And then your ticket answer would have but a simple "not possible". ... just wondering, after seeming to have understood the mechanism behind the way it currently works. 
Regards,
Carsten
You could also impersonate the Proxy User, and assign the original comment author if exists in the local system or use the proxy user if the user is not found.
Documentation: https://docs.exalate.com/docs/how-to-impersonate-a-comment-in-jira-cloud
We do sync between a JSM (Jira Service Management) and JSW (Jira Software) project as to not have the need for a big number of service agents. With the way Jira sets and uses permissions public comments on JSM projects can only be made by service agents. So either one enables all possible people as service agent (which would result in tremendous costs) or impersonation can't be applied. We read this doc page earlier but could not use the solution. Therefore my intention to at least change the displayed name of the builtin Exalate user to something more, uhm, convienent or "customer compatible".
Hello,
You could change the Proxy User, which is the work management system user used by Exalate to make changes. You can select an existing user as the Proxy user, or you can create a new user if you wanted the proxy user to be named "Ticket Robot"
In the following documentation you can find how to change the proxy user depending on the Issue tracker that you are using: https://docs.exalate.com/docs/proxy-user
Hello,
we are looking for a way to change the name of the user being used for synchronization. Currently, it’s labeled “Exalate” we think will confuse users. Web search did not provide helpful information. I found a page in your community pages (“Exalate Username change”) that reflects our request, but the answer was neither helpful (as to; provide the actual user in the comment) not the linked page available.
For us and now it would be sufficient to just change the name from “Exalate” to something like “Ticket Robot”.
Regards,