I can get why that user might have a pro-communist bias themself due to being from a pro-communist instance, but the articles they linked seemed to be an accurate enough representation of how the far left and far right see Wikipedia.
Maybe not completely accurate to how it really is in all aspects, but I don't really care enough about Wikipedia's biases to fact check each contradictory claim in each article. I barely use it as a point of reference anymore anyways. (Though I've found it tends to have a liberal bias, like both the articles stated. I seem to remember that during the past election, some sections of the articles about Trump or featuring him in some way used very emotionally charged language)
But accurate or not, I still find it hilarious to look at the articles side by side. One claims the articles are written mainly by teenagers and the unemployed and supports communism, and the other claims they're written mostly by privileged White men who hate communism.
That's a really good site too, though I suggest using fedipact.veganism.social if you're specifically interested in which instances are defederated from Threads. Some instances have hidden blocklists and won't show if they have defederated Threads if you search through defed.xyz.
For example: You can only see that retro.pizza and masto.ai have hidden blocklists if you look through defed.xyz. However, if you look on fedipact.veganism.social, you can see that retro.pizza has joined the Fedipact against Threads, while masto.ai is fully federated with them.