Kosh did not speak "Entil'zha Valen"...
Exactly right. In fact, when they shot the pilot Kosh had no spoken lines at all. The reference to Kosh's "thought balloon" had been cut at an earlier script stage because JMS thought it might be too much of a spoiler (since he expect to go right into production on the series and the first episode to debut the week after the pilot aired.) So no voice actor was even cast for the Kosh role at that point.
Ardwright Chamberlain only recorded the line years later when TNT provided the funds to re-edit the film, complete, correct, and add to the CGI and restore deleted scenes, etc. Since the revised version of
The Gathering was to air on the same night as
In the Beginning, just a couple of weeks before the start of S5, the spoiler issue no longer seemed like such a big deal.
Regards,
Joe