The object name is too long in NFD/NFC when connected to Teradata Error occurs when you use SQL comments above the SELECT statement within the Connect In-DB customer query box. Once the comments are removed the problem is resolved. Pity I cant use comments though.
Looks like nobody addressed your issue. I have ran into the NFD/NFC issue many times in Alteryx and has nothing to do with comments. Your issue and the same I run into often is with Alteryx's SQL editor as it inserts or modifies the characters, especially with spaces by compressing. It has been an editor issue since day one.
To resolve, edit your SQL and make sure you insert spaces after each line, especially the "SELECT", I guarantee that is causing your issue. Now we can close this out.