Comments. Are. Disposable.
Moderators doing are encouraged by SE to delete comments for any number of reasons. Frankly SE employees have deleted far more comments than us Pro-Tems have yet -- they delete reams and reams of stuff and then point us to their work for how it's supposed to be done.
However we are encouraged to leave 'breadcrumbs' that show were things have been removed and why. I do this (almost) all the time and I see most other mods do the same. In this case a comment didn't get left and we'll be sure and mention it to that mod.
However, moderator intervention is not the only way comments get deleted. When a comment gets flagged a moderator is notified and we can intervene and do clean up, but if we choose to do nothing and a few more flags collect, they will get automatically get deleted. Any time a comment gets 3 flags from the community (as, so 'obsolete') it will get automatically deleted without a moderator stepping in.
If you want to have a discussion with an OP, invite them to chat, then link the chat conversation later. Every message, room, and even delineated conversations inside rooms have permalinks. Chat messages are typically NOT deleted. Unlike comments, chat is a permanent record of a conversation on a topic.
Lastly, even though I wasn't the one who did comment cleanup there, I can see why it happened. There was a whole string of comments basically bashing on people rather than constructively suggesting corrections or improvements. If you have something that you think should be fixed that did not get addressed in the edit, feel free to comment again. Keep it focused and keep it respectful. However the best place to do this is probably not a comment, but an answer. The OP suggested you try to represent the view you were commenting from in an answer. Answering a question in order to point out a false premise has, historically, been accepted as a valid operation as long as you then go on to answer the question as best it can be with the premise corrected.