Visit a mobile talk page e.g https://en.m.wikipedia.org/wiki/Talk:David_Lammy. Scroll down to the bottom and the "Read as wiki page" link
Expected behaviour:
- Only border is 1px solid #eaecf0 on top
Actual behaviour:
- Has bottom and side borders from browsers default button styles
Guessing this is a side effect of T205341: Replace reset.css rules with ResourceLoaderSkinModule `normalize` feature