It is impossible to like posts even when executing javascript on the forum.
Many icons, among them post interactions, are also invisible.
This is an issue with Discourse, as other forums based on it have the same behavior.
Changing security settings within Tor Browser is trivial, but it affects all open tabs, which may not be what the user wants.
I think on our end there is little we can do.
My suggestion for you would be to use the compartmentalization features of Qubes and create a VM with tor browser, with a less strict security setting, but which you only use to visit discourse fora.
And since you do login, one might as well turn on cookies to save the session and avoid the annoyance of having to login.
Just an idea 
Yes that has been my go-to, binds for disposableVMs of all kinds. And non-dispVMs with some customisation for single use-cases.