text-align: inherit for th is centered in Safari, align to the start of the block in Chrome and Firefox

[karlcow]

https://html.spec.whatwg.org/multipage/rendering.html#rendering

User agents are expected to have a rule in their user agent style sheet that matches th elements that have a parent node whose computed value for the 'text-align' property is its initial value, whose declaration block consists of just a single declaration that sets the 'text-align' property to the value 'center'.

• Safari https://bugs.webkit.org/show_bug.cgi?id=138577
• Chrome https://bugs.chromium.org/p/chromium/issues/detail?id=431867

From top to bottom: Safari, Chrome and Firefox (latest versions)

Minimal test case

data:text/html,<!doctype%20html><table><tr><th%20style="text-align:inherit">START</th></tr><tr><td>AAAAAAAAAAAAAA</td></tr></table>

BootStrap expected the case of having things aligned on the left, hence they used text-align: -webkit-match-parent to force the alignment.
twbs/bootstrap#30321 (comment)

[annevk]

cc @whatwg/css