I'm assuming he is talking about the biker gang episode, in which case he is probably talking about the F-word (meaning the slur against gay people).
Personally, I think having a filter against slurs is not unreasonable

Somewhat.

If the poster themselves removed it, then no - these usually shows up as "deleted" rather than "removed" (but not always). Sometimes apps that don't properly pay attention to the removal request can still see these, but I know of no effective way to view these routinely, short of spinning up your own instance and archiving not only every post and comment but also all of their edits as well.

For mod removal, you can check the modlog (for your instance here, or the one for Lemmy.World, both of which theoretically should show the same contents, but in practice they don't for whatever reasons). Note that is the entire modlog for the entire Fediverse, so it requires filtering to find the specific post/comment that you want to know about. The Lemmy devs could help people see the modlog much easier, but they don't. They don't seem too big on such democratic efforts, and very often simply ban people outright, from the entire instance including communities they've never once visited, if you ever criticize what they say or if you say something that they do not agree with. Though they did recently release a feature to allow mods to do this - further increasing the power of the establishment, while leaving common plebes like us to have to filter the modlog (which also can hide the identity of the mod who removed it).

Ergo, I would not hold my breath waiting for this feature. At least not on Lemmy, but perhaps from the more democratically-managed PieFed or Sublinks or Mbin or such... I could really see that happening for those?

Edit: oh but for text like the "removed", hell no, that's also a lost cause - at least, again, on the Lemmy codebase, unless you use an instance that decides not to implement the language filtering.