Although this user acknowledges the logical fallacy ad populum, they do not think that it applies to human language, and recognise that the majority determines grammatical "right" and "wrong".
hän hänet hänen hänself, hänselves
If this user could come up with standard words to replace the singular they, them, their, and themselves/themself, they would respectively be hän, hänet, hänen, and hänself, hänselves.
couldn't've
This user believes that couldn't've would make a perfectly fine word.
subj
This user prefers that the subjunctive mood be used. Were this user you, they would use it.