Note that Malosi only blocks status effects and stacks from being casted.
This does not include:
- Direct heals
- Dispels or removals
- Health boosts
- Minion summons or minion effects
- Mana reductions or direct Mana increases (such as Misandra’s)
For what is considered a status effect, please see the first post in the linked guide. All that will be blocked from being casted.
I’ll be working on adding in a section for Stacks in my current Status Effects guide, in the near future as well 
Look forward to it!
Currently Mireweave from Season 3 is the only hero who has a stack. This is blocked from increasing if she uses her skill subsequently under Malosi’s ailment.