The #a... part is an anchor to specific answers or comments, and appears in the "Recent questions and answers" and "All activity" feeds. It happens there because they are feeds of comments and answers, so naturally the links go to the comment or answer referenced in the post.
If you want it without that, just use the questions feed, e.g. http://question2answer.org/qa/feed/questions.rss
You can turn the other feeds off in Admin options.
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask here, in English.
To report a bug, please create a new issue on Github or ask a question here with the bug tag.
If you just want to try Q2A, please use the demo site.
April 20, 2021: Q2A 1.8.6 released!