In Mongolian script, U+180E (MONGOLIAN VOWEL SEPARATOR) is used within a word, which is not a word boundary. Converting them to space is not correct. According to English Wikipedia,

A separated final form of vowels a or e (᠎ᠠ ‑a/‑e) is common, and can appear at the end of a word stem, or suffix. This form requires a final-shaped preceding letter, and a word-internal gap in between. This gap can be transliterated with a hyphen. ... The presence or lack of a separated a or e can also indicate differences in meaning between different words (compare ᠬᠠᠷ᠎ᠠ qar‑a 'black' with ᠬᠠᠷᠠ qara 'to look').

Steps to replicate the issue (include links if applicable):

• Go to ᠬᠠᠷ᠎ᠠ in English Wiktionary
• It redirects to ᠬᠠᠷ_ᠠ (note the space)

Also,

• Create a page with U+180E in title
• The character in title will be converted to _ (space)