The person who laughs along may be postponing a conversation they do not know how to begin.

Laughing along can be a way of postponing something. The comment landed badly, and objecting would require a conversation you do not have the words for, so the laugh buys time and costs a little each occasion. Nobody in the room learns that anything happened.

If you keep doing this in one particular situation, it is a signal worth taking seriously. You do not have to confront it in the moment, which is usually the hardest possible place. Say it later, one to one, in whatever imperfect words you have. And if someone tells you something you said did not land, receiving it without defending yourself is most of the job.