Umbrella issue to track multiple bugs.

Reported on Meta.SE in the following posts:

• https://meta.stackexchange.com/a/360038/395497
• https://meta.stackexchange.com/a/360050/395497
• https://meta.stackexchange.com/a/360153/395497
• https://meta.stackexchange.com/a/380383/51 - formats based on escaped md symbols
• https://meta.stackexchange.com/a/380381/51 - lang-* doesnt work in RT, works on site
• https://meta.stackexchange.com/a/380339/51