With a lot of sites I have to press tab ~7 times in order to get to the input that I want to use. I'm thinking that I will set the tabindex on that input to 1 so that it gets focus first. It seems like an upgrade. Any downsides?
In order to comply with WCAG accessibility guidelines, the tab order of your site/app should follow the visual order of the page, so left to right (or right to left if the language is rtl) and top to bottom. Failing to comply with this guideline (2.4.3) would be an downside to your proposed solution.
The WCAG has another guideline (2.4.1) related to your issue which is to create a way for keyboard/screen reader users to bypass repeated navigation on the screen.
This usually comes in the form of a skip link. A skip link must be the first focusable element on the screen, and activating it would move the focus to the first focusable element within the main content. Often, the link will be hidden by default and only visible when focused. Progressive has a great example of this on their site.
No - seems great. Fast solution - no useless info.
If you use tab in this post (First - tags active - later actions - your avatar - nick - and action add a comment)
question: what is the demand of users, tags, options or viewing your profile?
Is it worth skipping 9 actions - to reach 10 ultimately the most adequate (add a comment)?
However, in the case of inputs, I think that there are not many potential affordances, so the action is most justified by practical use.