1) They could be looking to accumulate cheaper shares throughout the whole day
2) SDL is liquid and has a $1 billion + market cap. If (the manipulators) don't act during the day, then the best they'll be able to achieve during the close of the day is the difference in a 0.5 cent increment (i.e. closing at 38/38.5 or 40/40.5). This would not do much good if during the day SDL has already run up 5% or so.
3) If a company is wanting to take-over SDL they would not be happy to see the daily share price rise, when the fundamentals are not changing.
*I am not suggesting that a company is actively pursuing number 3, but number 1 looks likely, as why else would somebody make a separate trade of 2 shares to play with the share price. (Surely that can't be considered a hobby for fun reasons.)
SDL Price at posting:
40.5¢ Sentiment: Hold Disclosure: Held