@Kii’s method is how I get it.
My first tab shows the correct pink heart. The screenshot here is of the second open tab. If I look closely, it shows that I liked @Kii’s post, but the heart is still greyed out:
and if I try to like it again, I get scolded:

(In my case, it’s usually because I opened a link directly from the BBS page without switching directly to it, forgot I did that, then opened the same link from the article on the main BB page. For this test, I just copied/pasted the link into a fresh tab.)
(Win7 Pro, Brave browser)
(Edited to add: same effect in the current Pale Moon Portable (29.4.4.win32). Sorry for the delay; my installed version on Pale Moon turned out to be a bit behind the times, BBS-wise.)
