About the "Bug Reports" section, you can add topic sub-pages to your main project page, like in this other project page (look at the bottom page, section "Community" posts): https://r00k.itch.io/rust-dust; By clicking the "Bug Reports" topic link (this one created by me), you will be redirected to a new page where you can see it's possible to add new posts clicking on "New Reply" button (or "Post" button at the bottom page), and reply to each new message like with a regular comment (with the exception of the first message so that it can be used to describe the topic purpose and, for istance, the bugs posting segnalization rules).
However, it has to be noticed that, for now, itch.io make you choose in the project edit page, section "Community", between have only a section for simple comments or an organisable/plain section for Community topics (discussion board), not both a the same time. So, switching to the second option, you will have a confusing plain list of topics, one for the Bug Reports, and every other one for every single comment.
Also I've make some test in a Community topic organization, trying making categories and sub-categories for Bug Reports and regular comments, and I have to say that it's a little confusing to use and buggy.
Maybe in the future they'll add the ability to create a separated section only for Bug Reports, as they have already done for the "Develog Section".
We will see...
Thanks for the attention.