Update Trigger Assistance - Update Same Row More than Once?

Good morning,

I'm new to Triggers and am not understanding why this is not working.  I've tried the web and none of the articles seem to answer my question.  What I'm trying to do is clean a string and standardize some data the users input into a 1000 character varchar field.  I have a source table which has a trigger on it that inserts a limited number of columns that we'll use for reporting purposes.  After the row has been inserted into the table (referred to as "destination" in the code block), I'm looking to update the comments string, capitalizing the first character of the string, standardizing spacing after a colon, removing hyphens at the beginning of the string.  The source and destination tables both have the comments field as a varchar 1000, not null data type with a key id between the source and destination tables.  At another segment of our system, there were errors reporting nulls and when this was removed, everything cleared up.  I can do a series of replace statements when the data is required in reports but would rather have it clean in the destination table.  The code is below:

CREATE TRIGGER [dbo].[destination_Update_trg]
ON [dbo].[destination]
AFTER UPDATE
AS
BEGIN
	SET NOCOUNT ON;
			IF EXISTS (SELECT	*
					   FROM		destination C
								JOIN INSERTED I
									ON I.PrimaryKeyID = C.PrimaryKey
					   WHERE	I.Comments IS NOT NULL AND I.Comments <> '')
								BEGIN
									UPDATE	T
											SET T.Comments = 
												CASE 
													WHEN T.Comments <> '' AND LEFT(CAST(T.Comments AS VARCHAR (1000)), 2) LIKE '- %'
													THEN SUBSTRING(T.Comments, 3, 1000)
												END						
									FROM	destination T
											JOIN INSERTED I
											ON T.primarykey = I.primarykey
									WHERE	T.primarykey = I.primarykey
									UPDATE	T
									SET		T.Comments = UPPER(LEFT(CAST(T.Comments AS VARCHAR (1000)), 1)) + SUBSTRING(CAST(T.Comments AS VARCHAR (1000)), 2, 1000)
									FROM	destination T
											JOIN INSERTED I
												ON T.primarykey = I.primarykey
									WHERE	T.primarykey = I.primarykey
									UPDATE	T
											SET T.Comments = REPLACE(SUBSTRING(T.Comments, 1, 1000), ': ', ':  ')-- '[A-9]:  [A-9]'

									FROM	destination T
											JOIN INSERTED I
											ON T.primarykey = I.primarykey
									WHERE	T.primarykey = I.primarykey
											AND SUBSTRING(T.Comments, 1, 1000) LIKE '%[A-Z]%: [A-Z]%'
								END
					
					
RETURN
END;

GO