You are using HTTP POST instead of GET when submitting edits, correct? I believe that may be part of the problem.
It is seemingly being updated fine (the text gets put there), but it is being interpretated as text, not wikitext (so the tags are being ignored)
Optionally, try to recreate it by the link I sent in original email - All the params used is there, aswell as the text attempting to be updated (in 'GET' format).
I made the request using the 'api sandbox', and additionally tried it directly in browser.
- Ah, the problem is you should be using POST when editing (or anything that requires a token). --Pcj (talk) 11:52, 11 October 2018 (UTC)