1) I’m assuming you’re referring to the emoji buttons. They are useful to determine upvotes and downvotes on issues and merge requests. These counts can be used when sorting for popularity. We leverage system emoji here and in most cases they are a bright yellow (https://emojipedia.org/thumbs-up/). It’d be possible to use our custom icon library (http://gitlab-org.gitlab.io/gitlab-svgs/?q=thumb-) for these buttons, but then they wouldn’t visually align with other award emoji that can be added inline. Here’s more info https://docs.gitlab.com/ee/user/award_emojis.html.
2) If you don’t have permission to close the issue (or merge request), you will only see the 'Report abuse' button (I’m guessing this is what you’re seeing), otherwise there would be a split button with 'Close issue' as the default option, and 'Report abuse' as the second. I agree that this needs some further consideration, so I opened an issue to start a discussion https://gitlab.com/gitlab-org/gitlab/-/issues/223775. Feel free to contribute and add your thoughts there too.
3) A few things are at work here. We recently updated our neutral palette to normalize it with the rest of the color palette, and address some accessibility items. We’re working on updating the neutral variables and remap them throughout the product, see https://gitlab.com/gitlab-org/gitlab-ui/-/issues/627 and https://gitlab.com/groups/gitlab-org/-/epics/2964. If there’s anything you don’t think would be addressed by those changes, it’d be great if you could open a new issue (https://gitlab.com/gitlab-org/gitlab/-/issues/new) and cc the UX designers (@gitlab-com/gitlab-ux/designers). Regarding buttons, we are in the process of replacing deprecated buttons in the product with new ones from GitLab UI https://gitlab-org.gitlab.io/gitlab-ui/?path=/story/base-but.... Here are a few issues covering that effort https://gitlab.com/gitlab-org/gitlab/-/issues?scope=all&utf8.... Many other issues will be created to do the same in other parts of the product.
I hope this helps, thanks again for your comments!