I've given plenty of explanation, wrote many notes about it. You may have not read them because maybe you don't follow me or your client didn't bother to fetch them from my relays.
Discussion
Your client (presumably a real one) is including both of these tags:
[
"e",
"d1d65af7f31e675e6addd8586b195a52d123224256530a70681066ca2947a523",
"mention"
],
[
"e",
"9919c19ef2bc6d3bc3dfe7b9fb8b6fe5ac1d62048871210ba9eec313bb1388e4",
"",
"mention"
]
One is straight up malformed (the "mention" marker appears in the wrong position).
The other one means a quote is being mentioned or embedded (effectively the same meaning as the "q" tag).
The referenced note is one above in this thread: nostr:nevent1qvzqqqqqqypzqwlsccluhy6xxsr6l9a9uhhxf75g85g8a709tprjcn4e42h053vaqqsfjxwpnmetcmfmc0070w0m3dh7ttqavgzgsufppw57ascnhvfc3eqj3mfsq
I suppose you didn't mean to mention that note, much less through a malformed tag.
I read one of your posts, and you displayed a lack of understanding of the features of those 3 apps in particular.
The biggest use of Nostr will be adding it to existing projects, not building new projects from scratch.