Avoid overloading web standard slots?

[mayank99]

Now that declarative shadow DOM is available cross browser, it might be a good idea to respect <slot>/slot= inside WebC templates.

Web's own slots could be renamed to something like <webc:slot>/webc:slot=.

Similarly, WebC could avoid doing special handling of <template> by default. I've encountered very strange issues when creating WebC wrappers over <template shadowrootmode="open">.

See also: #185