I have a mod (self-written) that is bare-bones and ‘fixes’ this issue. It should be available on curseforge ‘soon’.
The only issue with this fix is, while it makes a valid link, the icon someone sees when they click on the link will be a question mark.
This should have been under my main Obikaren, but I’m under-caffeinated and didn’t notice.
If nothing still works soon, I’d use it!
Available on curseforge now. Search for ‘obimount’.
What? Yes, it is named after my toon… >.>
Thank you for posting this!
Spread the word, if ya know anyone else suffering from this issue.
Best we can do are bump posts and share the word in game 
Having this same issue, i saw other threads about this but customer service just keeps closing down threads that are left unresolved or they will give the same generic responses of reset your UI yada yada.
Also having this issue but only on one character, the other characters don’t seem to have this issue. Have tried everything suggested in this thread with no results - it’s only the mounts I cannot link, so disappointed.
The addon might be the only fix!
its a nice to have a work around but if a addon can fix it then so to can Blizz.
That’s true, it IS Blizz though 
Some things are broken for a little too long!
The fact that the addon works I thank you sir!!!
Blizzard fix this though like it took an addon auth to fix YOUR problems… wait why does this not surprise me…
Thank you for that, I couldn’t link any mounts on my remix character and this fixed it instantly!
You’re a saint and my hero, had this happening for a few months and tonight finally got sick enough of it to look up something and found this. Works great, great job
Big L to blizz for ignoring this bug
I just ran into this problem today, so Blizzard still hasn’t fixed this…
I tried installing the ObiMount AddOn that you so kindly created, but it’s out of date – any chance of an update? Regardless, thank you for your time in fixing a problem that they have yet to deal with! <3
is it not working for you? might be out of date but still works for me.
Im reviving this thread. Still having the issue and the addon Obikaren gave us “Obimount” seems to be the only solution.
Obi, if you still check in on this thread, you’re our only hope, man. The mod still works for TWW, but it’s 5 months old since its last update. If Blizzard can’t fix their own crap, you can.
I just tried linking mounts and it seems to work now – and I don’t have the ObiMount AddOn turned on (I installed it weeks ago and totally forgot to actually turn it on -__-"), so it seems like it’s fixed… for now.
I am also having this issue (since about December of 2023) - I’ve done all the things…including a full re-install. I can link pets, armor, weapons, etc. just not mounts. I get the weird link text in the chat window. I’m only posting so that maybe Blizz…er…Microsoft will fix it.
Been having this issue past few days. Typically exclusive mounts (Ksm ones eg).