IIRC, I cleared the flag and put a response to you in the system explaining the reason: there is no policy on this as far as I know, so users are free to post multiple answers, if you think they should be combined you should ask their author directly to combine them (which you haven't done yet) and not the moderators.
Editing other people's answers in a significant way is not uncontroversial. I don't remember any case of merging of answers in the way you are suggesting. Moreover, it is not uncommon to answer new issues that arise in comments in a new answer.
If you ask me what you should do if you want them to be combined, I would suggest asking the author to combine them. If the author doesn't want to then I suggest leaving it as it is. If you really want to have the material in the answers combined in one answer then you can post a new answer yourself (possibly in a CW one).