Can you see if a moderator has removed comments from a thread?

Yes, but it involves sorting through the community modlog.

I wonder if this feature could be implemented -- it would just be another sorting option in comment sections -- assuming that the server actually stores this data.

Can you see the content of the removed comments?

No. Not even mods/admins can.

From what I can see in the modlog, it appears that you can see the content of comments, but just not the content of posts. It seems to treat comments as post titles in the log. What's also weird is that they have links associated with them which appear to point at nothing. Perhaps they are supposed to point to the original comment/post?

Are moderators able to specify motive for the specific removal?

Yes, but to be honest, I have no idea where that reason goes or who it is visible to

It looks like you can see it underneath the removed item in a little bit of text that states "Reason", and then the reasoning.