

AFAIK it’s a fedia (mbin) compatibility issue with Lemmy in general, some links posted aren’t federated properly and instead just show up as the thumbnail image from Fedia.
Probably something that is going to be, or already is, fixed in a newer Lemmy version, but some instances are a little slow to update.

If you want to make it singular like he/she/it, then make it singular.
He has a car, she has a car, they has a car.
He was friendly, she was friendly, they was friendly.
He sounds fine, she sounds fine, they sounds fine.
Notice the issue?
A singular they is an okay concept, but you then have actually allow it to be singular, in every use - a direct replacement for he/she with no other word or sentence changes necessary.