[haZh]

There might be an .amx plugin interfering with the default chat. Search for it remove it from the plugin list.

On a side note though, if you have a proper wall hack blocking system (or taken care of them somehow), I don't see any harm having it on a public server. Mostly on big maps so dead players can notify where alive players are. Plus the server will be more fun looking how the dead react to you, but meh just an opinion.