halacha - Must the spacing between words in a written Torah be consistent?

I'm asking this question with some emphasis on the beginning of parshat Vayechi.

Most chumashim that I have seen have a notation that unlike the end of every other weekly Torah reading that has a paragraph break (either with next week's portion continuing on the same line, or on the next line), there is only one-letter's spacing between the end of Vayigash and the start of Vayechi,

In other words (no pun intended), if one were to look in a torah, he would see the word me'od and then the next word would be Vayechi, immediately following.

I've seen a number of Sifrei Torah add some extra spacing before writing the word Vayechi. It is not that much spacing that it becomes to look like a parsha stumah (closed), but it also doesn't appear like it's immediately the next word, as is the writing of other words in a verse. It is as if the sofer intentionally wanted to add this extra spacing to make Vayechi stand out.

Is this technique alllowed - to intentionally add extra spacing when one shouldn't? In general, shouldn't a sofer aim to have uniform spacing between words throughout the entire Torah? When and how much leniency might be allowed in word spacing?