you can disable hover actions in Gmail:
Settings -> General -> scroll to "Hover Actions" -> click on "Disable hover actions".
That way the "Accept invitation" button will at least be always visible and you will not click on it by mistake.
Solved by my friend Ranko, I am just posting the answer.
I assume you have added the custom domain account in your personal account's Gmail settings / Accounts and Import / Send mail as settings. Click edit info there next to custom domain account, and uncheck Treat as an alias.
If you uncheck the box: Replying to messages from the other address
adds that address to the To: field.
Moving multiple messages to another folder from a list of search results is super easy and fast. You just need to do a couple more clicks than the "Move To" option elsewhere in Gmail:
Select the conversations you want to move from the search results page.
Apply the LABEL that you want to move the conversations to from the "Label" icon (now they're labeled, ...