Sorry, not quite correct or natural. If you are talking about responding to bad words, REPLIED and COMMENTED both need prepositions in this case: Bad words will be replied to below the photo (still a little awkward) Bad words will be commented on/upon below the photo. If you are actually talking about placing the bad words, you'd need to say it another way. Something like: Bad words will be posted in the comments below the photo. There will be bad words in the comments below the photo. The comments/replies below the photo will have bad words in them.

It doesn’t make sense. I have no idea what you mean by ‘bad words’ and ‘replied’. You can’t ’reply bad words’. ‘Bad words’ is an expression used when talking to children. They are always discouraged, never encouraged.

The phrase "Bad words will be commented below the photo" sounds more natural than "Bad words will be replied below the photo." A clearer way to convey your meaning would be: "Bad words will be left in the comments below the photo." This indicates that inappropriate comments will be posted under the photo.