The bug is also in version 6.21
Maybe I should clarify what I mean. Although you can use the -t option in $read to specify that the line should be treated as text, this option is not available in the /play command.
The only workaround here is to "play" commands with the -c option and read the text.
Another thing I would like to add is that if /play is using $read internally, this should probably be replaced with a /fopen $fread /fclose loop.
Note: the $read help file section says:
If the first line in the file is a number, it must represent the total number of lines in the file. If you specify N = 0, mIRC returns the value of the first line if it is a number.
If the t switch is specified then mIRC will treat the first line in the file as plain text, even if it is a number.
This was added in the very first version of $read in mIRC v3.6 in 1995.