I’m about to finish up the ribbing part of a sweater and before I move on to the body, I need to increase 35 stitches evenly on the last row of ribbing which is a wrong side row. This ribbing is k1 p1, but the knits are all in the back loop. After this, I’ll have one row of normal stockinette before I move into working several cables. Should my increases match the twisted knitting of the ribbing or match the stockinette I’ll be starting on the next row? Also, when increasing in ribbing, is it better for the right side to have added purls or added knits? I’ve always wondered that.
Increase in twisted ribbing?
Well, you could do what I did just now and make a swatch trying the different approaches. 
What I think I would do is to inc in the WS row as it says, keeping the k tbl and just using a backward loop increase when needed for the inc.
If you want to inc in either the knit or the purl I’d inc so that the purls are increased on the right side, they will recede and not be so noticeable.
You know, what Merigold says makes sense for the increases in purls receding and yet I always increase on the RS knit sts (so on the WS purls). The increases in knit seem to disappear into the next row of knit sts. I think increasing on the next row works fine too. I’ve done that as well. Maybe you just have to try a method and see if you like it.