Capitalization certainly has different usages in different contexts - I think we can all agree on that. If I were to say:
Jan, THANK YOU for all of your work on Dutch profiles.
Am I yelling or making an emphasis? Possibly both! It all depends on the context.
With that said, it should be noted that the text you are referencing as 'yelling' is actually a button that has a style class assigned to it. It is the same style as other buttons, such as:
DESCENDANTS, ANCESTORS, ASK QUESTION, INVITE, COUSIN BAIT, TREE & TOOLS, POST NEW COMMENT, SAVE CHANGES...
If you know about HTML and CSS, then you will know it is much easier to manage a small range of CSS classes that can be reused, rather than making CSS styles for each and every function, or applying specific styles to specific areas that override the default behaviors. This would result in longer production and update times for simple changes due to the need to test every possible scenario, or adjust elements that may start acting differently, etc.
So I guess my statement here is: If you also object to the use of capitalization in the other cases (buttons) I mentioned above, then I would suggest making a proposal to change the styling, rather than trying to draw conclusions about what is yelling or emphasis.