Just to make it clear: everyone can do whatever he/she wants with his/her own posts. I am just (kindly) asking you to stay in topic for this steemstem post: gravitational waves. This holds for you as well as for anyone else as well, and I would answer the same thing to anyone else. It is not because there is a part of the comment on-topic that one should promote a post on a different topic.
PS: You are free to treat your own posts in this way. I do the same with my own and after some time, the amount of irrelevant links posted as comments to my posts is close to 0.