Most platforms usually have a filtering system in place to help weed out such comments, and YouTube is stepping up their efforts in helping creators block such comments. The company has recently introduced a new feature which will help creators block spam comments that contain links. This means that whenever a comment is posted that contains a link, it will be sent to the user’s “Held for Review” section.
This means that the creator will have to manually approve these comments before they can appear in public. Depending on the popularity of your video/channel, the number of comments will naturally vary, but we guess it will help to keep certainly spammy links out of the general comments.
Note that this is an opt-in feature meaning that users will have to turn it on themselves, as opposed to it being enabled automatically. Details on how to enable it for your YouTube channel can be found on the YouTube Help Forum.